Devices with protected electrically-conductive metal grids

ABSTRACT

An electronic device has a touch screen comprising a transparent substrate having a first supporting side and an opposing second supporting side. The first supporting side of the touch screen has at least one electrically-conductive pattern, and a dry outermost polymeric coating disposed over at least part but not all of the electrically-conductive metal pattern. The dry polymeric coating has a dry thickness of less than 5 μm, an integrated transmittance of at least 80%, and a non-crosslinked thermoplastic polymer having a glass transition temperature (T g ) that is equal to or greater than 65° C.

RELATED APPLICATIONS

Reference is made to the following copending and commonly assignedpatent applications, all filed on even date herewith:

U.S. Ser. No. 14/______ filed by Bermel, Todd, Franklin, Mourey, andLandry-Coltrain and entitled “Electrically-conductive Articles withProtective Polymeric Coatings” (Attorney Docket K001794/JLT);

U.S. Ser. No. 14/______ filed by Bermel, Todd, Franklin, Mourey, andLandry-Coltrain and entitled “Methods for ProvidingElectrically-conductive Articles” (Attorney Docket K001908/JLT); and

U.S. Ser. No. 14/______ filed by Bermel, Todd, Franklin, Mourey, andLandry-Coltrain and entitled “Patterning Continuous Webs with ProtectedElectrically-conductive Grids” (Attorney Docket K001909/JLT).

FIELD OF THE INVENTION

This invention relates to electronic devices comprisingelectrically-conductive articles comprising one or moreelectrically-conductive patterns that generally include one or moreelectrically-conductive metal patterns. A dry polymeric coating isgenerally disposed over at least part of the electrically-conductivepatterns for various protective and coloration features. The variouselectronic devices can have touch screen displays.

BACKGROUND OF THE INVENTION

Rapid advances are occurring in various electronic devices especiallydisplay devices that are used for various communicational, financial,and archival purposes. For such uses as touch screen panels,electrochromic devices, light-emitting diodes, field-effect transistors,and liquid-crystal displays, electrically-conductive films are essentialand considerable efforts are being made in the industry to improve theproperties of those electrically-conductive films and particularly toimprove metal grid or line conductivity and to provide as muchcorrespondence between mask design with resulting user metal patterns.

Electrically-conductive articles used in various electronic devicesincluding touch screens in electronic, optical, sensory, and diagnosticdevices including but not limited to telephones, computing devices, andother display devices have been designed to respond to touch by a humanfingertip or mechanical stylus. Typically, touch screen technologyincorporates the use of resistive or capacitive sensor layers that makeup part of the display.

Typically, touch screen technology incorporates the use of resistive orcapacitive sensor layers that make up part of the display. There is aneed to provide touch screen sensors and displays that contain improvedelectrically-conductive film elements. Currently, such resistive andcapacitive touch screen displays use Indium Tin Oxide (ITO) coatings tocreate arrays used to distinguish multiple points of contacts. Effortsare underway in the industry to find useful replacements for ITOcoatings including the use of various other electrically-conductivemetallic compositions. ITO is in limited supply and exhibits undesirablefragility, lack of flexibility, and low conductivity compared to othermaterials.

As noted, touch screens are often prone to damage due to the increasedlevel of direct contact (touching) by the user of the display or frommoisture or water in the environment. Both resistive and capacitivetouch sensors can include translucent (or nearly transparent)electrically insulating covering materials disposed on the displaystructure in order to protect and isolate the touch screen sensors fromenvironmental conditions (such as moisture), abrasion, oxygen, and anyharmful chemical agents.

There is also a need to protect the electrically-conductive portions ofthe sensor from environmental damage (such as from moisture) and bothenvironmental and physical damage during manufacturing and integrationoperations.

Such electrically insulating covering materials include glass orpolyester layers as protective covers. Each of these materials hasadvantages and disadvantages. WO 2013/062630 (Petcavich) and WO2013/063051 (Petcavich et al.) both describe the formation ofcrosslinked polymeric protective layers over touch sensors (and displayscreens) using photocurable compositions containing variousphotoinitiators and photocuring materials.

U.S. Pat. No. 7,569,250 (Nelson) describes a process for applying aprotective coating to a flex circuit having conductive traces on onesurface and by applying a protective coating in substantially a liquidstate to the one surface from a roller including a protective coating ina patternwise fashion. Portions of the flex circuit are left exposed(uncoated) for connection to an electronic device such as a print headassembly. A protective coating can be applied to a surface of the flexcircuit and then further treated for example by crosslinking or thermalcuring.

While such materials can provide protective surfaces in touch sensors,it would be desirable to avoid crosslinkable materials because of theadditional processing procedure that is needed as well as the potentialproblems associated with photoinitiators or other crosslinking agentsthat may remain chemically reactive in the final protective surface andthat can cause yellowing if left as residue in the protective coatings.

In addition, residual photoinitiators used in photocuring operationsused to prepare protective coatings can pose adhesion and shrinkageproblems, at least partially due to their low molecular weight, highmobility, and likely high initial concentrations so that residualconcentrations after photocuring can be as much as 15% of the finalprotective covering weight. These problems can be particularly apparentin photocurable compositions that are applied to electrically-conductivepatterns using printing methods such as flexography at high curing andprinting speeds.

Thus, there is a need for improved protection of electrically-conductivepatterns especially when high concentrations of photocuringphotoinitiators are present so that yellowing and other problems areminimized.

SUMMARY OF THE INVENTION

The present invention provides an electronic device comprising a touchscreen comprising a transparent substrate having a first supporting sideand an opposing second supporting side,

the touch screen comprising on at least the first supporting side:

at least one electrically-conductive pattern, and

a dry outermost polymeric coating disposed over at least part but notall of the electrically-conductive metal pattern, the dry polymericcoating having a dry thickness of less than 5 an integratedtransmittance of at least 80%, and comprising a non-crosslinkedthermoplastic polymer having a glass transition temperature (T_(g)) thatis equal to or greater than 65° C.

In some embodiments, the electronic device further comprises anelectrically-conductive pattern disposed on the opposing secondsupporting side of the transparent substrate, and a dry outermostpolymeric layer that is disposed over at least part but not all of theelectrically-conductive pattern on the opposing second supporting side,the dry outermost polymeric coating having a dry thickness of less than5 μm, an integrated transmittance of at least 80%, and comprising anon-crosslinked thermoplastic polymer having a glass transitiontemperature (T_(g)) that is equal to or greater than 65° C.

In addition, some embodiments of the electronic devices of thisinvention comprise:

two or more of the same or different electrically-conductive patterns oneither or both of the first supporting side and the opposing secondsupporting side, and

the same or different dry outermost polymeric layer disposed over atleast part but not all of each of the two or moreelectrically-conductive patterns, each of the dry outermost polymericcoatings having a dry thickness of less than 5 μm, an integratedtransmittance of at least 80%, and comprising the same or differentnon-crosslinked thermoplastic polymer having a glass transitiontemperature (T_(g)) that is equal to or greater than 65° C.

The present invention provides a number of advantages. Because the dryoutermost polymeric coating is not crosslinked (or crosslinkable), thedry outermost polymeric coating requires no curing or post-processing,thereby reducing the complexity of the printing apparatus and process.In addition, the problems associated with photoinitiators and othercrosslinking agents, such as yellowing from residual reactants and otherproblems associated with post-curing chemical reactions are avoided. Inaddition, potential problems from shrinkage and adhesion are alsoavoided since low molecular weight materials (such as photoinitiators)are not required. Finally, the dry outermost polymeric layer is highlytransparent and can be properly used to cover all or only part of theelectrically-conductive patterns in the electronic devices so thatappropriate electrical connections can be achieved when desired.

DETAILED DESCRIPTION OF THE INVENTION

The following discussion is directed to various embodiments of thepresent invention and while some embodiments can be desirable forspecific uses, the disclosed embodiments should not be interpreted orotherwise considered to limit the scope of the present invention, asclaimed below. In addition, one skilled in the art will understand thatthe following disclosure has broader application than is explicitlydescribed with specific embodiments.

DEFINITIONS

As used herein to define various components of theelectrically-conductive patterns and dry outermost polymeric coatings,unless otherwise indicated, the singular forms “a,” “an,” and “the” areintended to include one or more of the components (that is, includingplurality referents).

Each term that is not explicitly defined in the present application isto be understood to have a meaning that is commonly accepted by thoseskilled in the art. If the construction of a term would render itmeaningless or essentially meaningless in its context, the termdefinition should be taken from a standard printed dictionary.

The use of numerical values in the various ranges specified herein,unless otherwise expressly indicated, are considered to beapproximations as though the minimum and maximum values within thestated ranges were both preceded by the word “about.” In this manner,slight variations above and below the stated ranges can be used toachieve substantially the same results as the values within the ranges.In addition, the disclosure of these ranges is intended as a continuousrange including every value between the minimum and maximum values.

As used herein, the term “photocuring” means the polymerization offunctional oligomers and monomers, or even polymers, into a crosslinkedpolymer network, in response to irradiation of such materials, forexample irradiation using ultraviolet (UV), visible, or infraredradiation at a suitable wavelength.

The term “photocurable” is used to define a material (or component) thatwill polymerize or crosslink when irradiated with suitable radiation,for example irradiated with radiation such as ultraviolet (UV), visible,or infrared radiation in an appropriate environment.

The term “polymerization” is used herein to mean the combining, forexample by covalent bonding, of a large number of smaller molecules,such as monomers, to form very large molecules, that is, macromoleculesor polymers. The monomers can be combined to form only linearmacromolecules or they can be combined to form three-dimensionalmacromolecules that are commonly referred to as crosslinked polymers.One type of polymerization that can be carried out in the practice ofthis invention is acid-catalyzed (cationic) polymerization utilizing thephoto-generation of acidic radicals. Another type of polymerization isfree radical polymerization utilizing photo-generation of free radicalswhen free radically polymerizable materials and suitable free radicalgenerating photoinitiators are present. In some useful embodiments ofthe present invention, both acid-catalyzed polymerization and freeradically polymerization can be used simultaneously in carrying out thepresent invention.

A “thermoplastic polymer” refers to a polymer that has no crosslinksites between individual polymer macromolecules and becomes liquid,pliable, or moldable above a specific temperature, and then it returnsto a solid state upon cooling. In many instances, the thermoplasticpolymers are also soluble in appropriate organic solvent media.

Recurring units in the non-crosslinked thermoplastic polymers describedherein are generally derived from the polymerizable units used in acondensation or free radical polymerization process, which polymerizableunits have the desired properties and contribute to the desired polymerT_(g).

Unless otherwise indicated, the term “mol %” when used in reference torecurring units in polymers, refers to either the nominal (theoretical)amount of a recurring unit based on the molecular weight ofethylenically unsaturated polymerizable monomer used in thepolymerization process, or to the actual amount of recurring unit in theresulting polymer as determined using suitable analytical techniques andequipment.

Average dry thickness of layers (such as the dry outermost polymericcoating) described herein can be determined from the average of at leasttwo separate measurements taken of a dry layer, for example, usingelectron microscopy, optical microscopy, or profilometry.

Similarly, the average dry thickness or width of lines, grid lines, orother pattern features described herein can be the average of at leasttwo separate measurements taken, for example, using electron microscopy,optical microscopy, or profilometry.

“Actinic radiation” is used to refer to any electromagnetic radiationthat is capable of producing photocuring or photopolymerizing action inaccordance with the present invention and that has a wavelength of atleast 200 nm and up to and including 1400 nm, and typically at least 200nm and up to and including 750 nm, or even at least 300 nm and up to andincluding 700 nm. The term “exposing radiation” also refers to suchactinic radiation.

The term “UV radiation” is used herein to refer to electromagneticradiation having a wavelength (λ_(max)) of at least 200 nm and up to andincluding 400 nm.

Weight-average molecular weight (M_(w)) is determined using SizeExclusion Chromatography (SEC). Values reported herein are reported aspoly(methyl methacrylate) equivalent weights.

Glass transition temperature (T_(g)) can be determined usingDifferential Scanning calorimetry (DSC) and values reported herein referto indium standards.

The terms “transparent” and “transparency” used herein in reference tosubstrates, polymeric layers including the dry outermost polymericcoatings, refer to materials and structures having an integratedtransmittance of at least 80% and more likely at least 90%. Integratedtransmittance is measured over the visible region of the electromagneticspectrum (for example from 410 nm to 700 nm) using a spectrophotometerand known techniques.

As used herein, the terms “electrically-conductive pattern” refers to apattern of electrically-conductive material, in a predetermined orrandomly arranged pattern that will have the function of carryingelectrical current. In most embodiments, such electrically-conductivepatterns are electrically-conductive metal patterns although otherelectrically-conductive materials can be used, such aselectrically-conductive polymers, carbon nanotubes, graphene, and otherelectrically-conductive carbon structures, can be used in otherembodiments. The electrically-conductive patterns can be composed ofmultiple regions, some of which are designed to be within a “touch”region of an electronic device (such as a touch screen sensor) intowhich the electrically-conductive article is incorporated. Other regionsof the electrically-conductive pattern can be outside the “touch” regionand arranged within border or electrically-connective regions. Suchregions can consist of electrically-conductive bus lines, probe pads,electrodes, and connectors. The connectors or connector pads as definedfor the present invention are the electrically-conductive regions of theelectrically-conductive pattern that will be connected to the externalpower connections, detectors, circuits, or other external components.For example, each electrically-conductive pattern can comprise an“electrically-conductive grid” or “electrically-conductive metal grid”that can be disposed in the “touch” region. The electrically-conductivepattern can also comprise an “electrically-conductive connector” or“electrically-conductive metal connector” outside the “touch” region andbe part of a connector pad. Still other regions can comprise otherelectrically-conductive lines and interconnections that provide pathwaysfor electrical current within the electronic device component.

Uses

The articles and methods of the present invention can be used in avariety of technologies and electronic devices including but not limitedto touch screen sensors, displays, integrated circuit components,microchips, thin film transistor components, and other display orfunctional devices that can be used in numerous consumer, industrial,and commercial products.

Touch screen technology can comprise different touch sensorconfigurations including capacitive and resistive touch sensors.Resistive touch sensors comprise several layers that face each otherwith a gap between adjacent layers that may be preserved by spacersformed during manufacturing. A resistive touch screen panel can compriseseveral layers including two thin electrically-conductive layers(usually metallic in composition) separated by a gap that can be createdby spacers. When an object such as a stylus, palm, or fingertip pressesdown on a point on the panel's outer surface, the two thinelectrically-conductive layers come into contact and a connection isformed that causes a change in the electrical current. This change inelectrical current from the touch event is sent to a controller forfurther processing.

Capacitive touch sensors can be used in electronic devices withtouch-sensitive features. These electronic devices can include but arenot limited to, televisions, monitors, automated teller machines, andprojectors that can be adapted to display images including text,graphics, video images, movies, still images, and presentations. Theimage devices that can be used for these display devices that caninclude cathode ray tubes (CRS's), projectors, flat panel liquid crystaldisplays (LCD's), LED systems, OLED systems, plasma systems,electroluminescent displays (ECD's), and field emission displays(FED's). For example, the present invention can be used to preparecapacitive touch sensors that can be incorporated into electronicdevices with touch-sensitive features to provide computing devices,computer displays, portable media players including e-readers, mobiletelephones and other portable communicating devices.

Systems and methods of fabricating flexible and optically complianttouch sensors in a high-volume roll-to-roll manufacturing process wheremicro electrically-conductive features can be created in a single passare possible using the present invention. Multiple printing members suchas multiple flexographic printing plates can be used to form multiplehigh resolution electrically-conductive patterns (or images) frompredetermined designs or patterns provided in those multiple printingmembers. Multiple patterns can be printed on one or both sides of atransparent substrate as described in more details below. For example,one predetermined pattern can be formed on one side of the transparentsubstrate and a different predetermined pattern can be formed on theopposing side of the transparent substrate. The dry outermost polymericcoating described herein can be incorporated or disposed over at leastpart but not all of each of the multiple electrically-conductivepatterns.

Outermost Polymeric Coatings

The outermost polymeric coatings used in the present invention arederived from mixing one or more non-crosslinked thermoplastic polymers(hereinafter “polymers” if not otherwise indicated), each or the mixtureof polymers having a glass transition temperature (T_(g)) that is equalto or greater than 65° C.

Useful non-crosslinked thermoplastic polymers can be used to providetransparent films as defined herein having an integrated transmittanceas described above.

Such non-crosslinked thermoplastic polymers can be condensation polymersincluding but not limited to, polyesters, polyamides, polyimides,polycarbonates, polyurethanes, polyureas, and polysulfones. More likely,the non-crosslinked thermoplastic polymers are addition polymers derivedfrom one or more ethylenically unsaturated polymerizable monomers, suchpolymers include but are not limited to, polyvinyl acetals,polyacrylics, polyacrylamides, polystyrenes, polyolefins, polyvinylhalides, polyvinylidene halides, polysulfones, and polyvinyl ethers.Naturally-occurring or synthetic cellulosics can also be used.

Useful non-crosslinked thermoplastic polymers can be linear, branched,comb., or any other known polymer topology. Also useful is block, graft,or tapered copolymers or polymers containing multiple monomers ofvarious topologies as long at the other properties described herein areachieved.

Particularly useful non-crosslinked thermoplastic polymers are“non-aromatic” meaning that no carbocyclic aromatic or heterocyclicaromatic moieties (or groups) are purposely incorporated within thepolymer.

Useful non-crosslinked thermoplastic polymers of this type includeacrylic polymers that are derived from at least one or more acrylate ormethacrylate ethylenically unsaturated polymerizable monomers. Suchmonomers are used to provide at least 5 mol % or at least 10 mol % andup to and including 100 mol %, of the “acrylic” recurring units in the(co)polymer based on the total recurring units. If the “acrylic”recurring units comprise less than 100 mol %, the remaining recurringunits can be derived from one or more ethylenically unsaturatedpolymerizable monomers that would be apparent to a skilled worker in theart, as long as such recurring units do not comprise carbocyclicaromatic or heterocyclic aromatic moieties or other functional groupsthat are capable of undergoing discoloration reactions. Thus, the usefulacrylic polymers can be homopolymers or copolymers that comprise two ormore different recurring units derived from two or more differentethylenically unsaturated polymerizable monomers.

Thus, the acrylate or methacrylate ethylenically unsaturatedpolymerizable monomers can comprise suitable ester alkyl groups that canbe unsubstituted or substituted with one or more alkoxy, hydroxyalkoxy,alkoxyalkoxy, or haloalkoxy groups. For example, such usefulethylenically unsaturated polymerizable monomers include hydroxyalkylmethacrylates (such as hydroxymethyl methacrylate), methyl methacrylate,ethyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate,n-butyl methacrylate, iso-butyl methacrylate, t-butyl acrylate, t-butylmethacrylate, n-hexyl methacrylate, n-dodecyl acrylate, 2-ethylhexylmethacrylate, 2-ethylhexyl acrylate, cyclohexyl methacrylate, cyclohexylacrylate, glycidyl methacrylate, glycidyl acrylate, chloromethylacrylate, or a hydroxyalkyl acrylate such as hydroxyethyl acrylate orhydroxypropyl acrylate.

In many embodiments, the non-crosslinked thermoplastic polymers arecopolymers (including terpolymers), each comprising recurring unitsderived from methyl (meth)acrylate (meaning either methyl acrylate ormethyl methacrylate) and recurring units derived from an alkyl(meth)acrylate wherein the alkyl has at least 1 carbon atom and up toand including 18 carbon atoms, wherein the recurring units derived fromthe alkyl (meth)acrylate comprise at least 5 mol % and up to andincluding 25 mol % of the total copolymer recurring units, and recurringunits derived from methyl methacrylate would comprise the rest of thecopolymers. Useful ethylenically unsaturated polymerizable monomers aredescribed above and others would be readily apparent to one skilled inthe art.

Other useful ethylenically unsaturated polymerizable monomers that canbe used to provide recurring units in the copolymers include but are notlimited to acrylamide, methacrylamide, acrylic acid, methacrylic acid,acrylonitrile, vinyl acetate, vinyl chloride, and vinylidene chloride,or any other ethylenically unsaturated non-aromatic polymerizablemonomer that is capable of copolymerizing with (meth)acrylates.

The non-crosslinked thermoplastic polymers can be prepared to have oneor more different types of recurring units derived from one or moreethylenically unsaturated polymerizable monomers described above, andsuch recurring units can be arranged within the polymer in any desiredorder, for example, randomly, alternately, in blocks, or otherarrangements that would apparent to one skilled in the polymericchemistry art.

The mol % amounts of the various recurring units defined herein for thedescribed polymers are meant to refer to the actual molar amountspresent in the polymers. It is understood by one skilled in the art thatthe actual mol % values may differ from those theoretically possiblefrom the amount of ethylenically unsaturated polymerizable monomers thatare used in the polymerization procedure. However, under mostpolymerization conditions that allow high polymer yield and optimalreaction of all ethylenically unsaturated polymerizable monomers, theactual mol % of each ethylenically unsaturated polymerizable monomer isgenerally within ±15 mol % of the theoretical amounts.

Some representative non-crosslinked thermoplastic polymers include butare not limited to, the following polymers wherein the molar ratios aretheoretical (nominal) amounts based on the actual molar ratio ofethylenically unsaturated polymerizable monomers used in thepolymerization process. The actual molar amounts of recurring units candiffer from the theoretical (nominal) amounts of ethylenicallyunsaturated polymerizable monomers if the polymerization reactions arenot carried out to completion.

Poly(methyl methacrylate-co-n-butyl methacrylate) 90:10 mole ratio;

Poly(methyl methacrylate-co-n-butyl methacrylate) 75:25 mole ratio;

Poly(methyl methacrylate-co-n-butyl methacrylate-co-methacrylic acid)85:15:5 mole ratio;

Poly(methyl methacrylate-co-hexyl methacrylate) 90:10 mole ratio;Poly(methyl methacrylate-co-octyl methacrylate) 90:10 mole ratio;

Poly(methyl methacrylate-co-lauryl methacrylate) 90:10 mole ratio;

Poly(ethyl methacrylate-co-n-butyl methacrylate-co-methacrylic acid)80:15:5 mole ratio; and

Poly(ethyl methacrylate-co-methacrylic acid) 90:10 mole ratio.

Many useful non-crosslinked thermoplastic copolymers and terpolymers arecommercially available. For example, poly(methyl methacrylate-co-n-butylmethacrylate) is available as ELVACITE® 4028; poly(methylmethacrylate-co-n-butyl methacrylate-co-methacrylic acid) is availableas ELVACITE® 2614; and poly(methyl methacrylate-co-lauryl methacrylate)is available as ELVACITE® 2552 from Lucite International. Other variousnon-crosslinked thermoplastic polymers can be either purchased fromvarious commercial sources, or they can be prepared using knownpolymerization techniques and known starting materials and organicsolvents. Where starting materials (such as ethylenically unsaturatedpolymerizable monomers) are not available commercially, such startingmaterials can be synthesized using known chemical starting materials andprocedures.

Preparation of Articles with Dry Outermost Polymer Coatings

In general, articles used in the present invention are prepared byfirstly providing a suitable transparent substrate having a firstsupporting side and an opposing second supporting side (the opposingplanar sides as opposed to edges). Suitable transparent substrates canbe composed of various materials.

Suitable transparent substrates include but are not limited to, glass(including flexible glasses), glass-reinforced epoxy laminates,cellulose triacetate, acrylic esters, polycarbonates, adhesive-coatedpolymer transparent substrates, polyester films, and transparentcomposite materials. Suitable transparent polymers for use astransparent polymer substrates include but are not limited to,polyethylene and other polyolefins, polyesters such as polyethyleneterephthalate (PET), polyethylene naphthalate (PEN),poly-1,4-cyclohexanedimethylene terephthalate, poly(butyleneterephthalate), and copolymers thereof, polypropylenes, polyvinylacetates, polyurethanes, polyamides, polyimides, polysulfones,polycarbonates, poly(methyl methacrylate), and other materials thatwould be readily apparent to one skilled in the art. Other usefultransparent substrates can be composed of cellulose derivatives such asa cellulose ester, cellulose triacetate, cellulose diacetate, celluloseacetate propionate, cellulose acetate butyrate, polyacrylates, polyetherimides, and mixtures thereof.

Transparent polymeric substrates can also comprise two or more layers ofthe same or different polymeric composition to form a compositetransparent laminate substrate. The transparent substrate can be treatedon either or both supporting sides to improve adhesion of any disposedlayers or electrically-conductive patterns. For example, the transparentsubstrate can be coated with a polymer adhesive layer, can be chemicallytreated, or subjected to a corona treatment, on one or both supportingsides.

Biaxially-oriented sheets, while appearing to have one layer, can alsobe provided with additional layers that can serve to change the opticalor other properties of the biaxially-oriented sheet. Such layers mightcontain tinting agents, antistatic or conductive materials, or slipagents as long as desired integrated transmittance is preserved.

The use of flexible transparent substrates for the manufacture offlexible electronic devices or touch screen components facilitates rapidroll-to-roll manufacture. ESTAR® poly(ethylene terephthalate) films,MELLINEX® poly(ethylene terephthalate) films, and cellulose triacetatefilms are particularly useful materials for making flexible transparentsubstrates including continuous substrate webs.

The transparent substrate can have a thickness of at least 20 μm and upto and including 300 μm or typically at least 75 μm and up to andincluding 200 μm. Antioxidants, antistatic or conductive agents,plasticizers, and other useful additives can be incorporated into thetransparent substrate, if desired, in amounts that would be readilyapparent to one skilled in the art as long as desired integratedtransmittance is achieved.

Electrically-conductive patterns (such as electrically-conductive metalpatterns) that can include electrically-conductive grids (such aselectrically-conductive metal grids) and electrically-conductiveconnectors (such as electrically-conductive metal connectors) can bedisposed on either or both of the first supporting side and the opposingsecond supporting side of the transparent substrate using any desirablemeans, of which there are several technologies known in the art.

Some electrically-conductive patterns can be composed from one or moreelectrically-conductive polymers, many of which are known in the art.For example, such electrically-conductive polymers can be selected fromsubstituted or unsubstituted pyrrole-containing polymers [as describedfor example in U.S. Pat. No. 5,665,498 (Savage et al.) and U.S. Pat. No.5,674,654 (Zumbalyadis et al.)]; substituted or unsubstitutedthiophene-containing polymers [as described for example, in U.S. Pat.No. 5,300,575 (Joans et al.), U.S. Pat. No. 5,312,681 (Muys et al.),U.S. Pat. No. 5,354,613 (Quinters et al.), U.S. Pat. No. 5,370,981(Krafft et al.), U.S. Pat. No. 5,372,924 (Quinters et al.), U.S. Pat.No. 5,391,472 (Muys et al.), U.S. Pat. No. 5,403,467 (Jonas et al.),U.S. Pat. No. 5,443,944 (Azoulay), U.S. Pat. No. 4,987,042 (Jonas etal.), and U.S. Pat. No. 4,731,408 (Jasne)]; and substituted orunsubstituted aniline-containing polymers [as described for example inU.S. Pat. No. 5,716,550 (Gardner et al.), U.S. Pat. No. 5,093,439(Epstein et al.), and U.S. Pat. No. 4,070,189 (Kelley et al.)].Particularly useful electrically-conductive polymers are those presentin their cationic form and comprise a polyanion, includingthiophene-containing polymers used in combination with a suitablepolyanion that can be a polyacid such as a polycarboxylic acid or apolysulfonic acid that is a homopolymer or copolymer. The disclosures ofall of these cited patents are incorporated herein by reference withrespect to the electrically-conductive polymers that can be used in thepractice of the present invention.

Some electrically-conductive patterns can be composed of one or moreelectrically-conductive carbon structures, many of which are known inthe art, including for example, conductive carbon black, carbonnanotubes, graphite, graphene, or combinations thereof.

In other embodiments, the electrically-conductive patterns are designedto have metallic characteristics. For example, photosensitive silverhalide technology can be used for this purpose to provideelectrically-conductive silver patterns on one or both supporting sidesof a transparent substrate, for example as described in U.S. PatentApplication Publications 2011/0289771 (Kuriki) and 2011/0308846(Ichiki). Additional silver halide technology used for this purpose isalso described in copending and commonly assigned U.S. Ser. No.14/468,626 (filed Aug. 26, 2014 by Lushington), the disclosure of whichis incorporated herein by reference. In such technology, silver halideemulsions can be designed on one or both supporting sides of transparentsubstrates, exposed through suitable masks, and the patterns formed bythis exposure can then be processed to form silver metal patterns andthe non-exposed silver halide emulsion is suitably removed. The variouselectrically-conductive silver patterns can be designed to have desiredpatterns using predetermined mask elements with corresponding patterns.

In still other embodiments, the electrically-conductive patterns such aselectrically-conductive metal patterns can be formed on one or bothsupporting sides of the transparent substrates using photocurablecompositions that can provide seed metal catalysts for electrolessplating processes. For example, the photocurable compositions cancomprise acid-catalyzed photocurable chemistry, free radicalphotocurable chemistry, or both types of chemistry, examples of whichare described below, but the present invention is not limited to thedescribed photocurable chemistries and can be carried out using anyknown photocurable compositions that can further comprise seed metalcatalysts that are suitable for electroless metal plating processes.

Acid-Catalyzed Photocurable Chemistries:

In some embodiments, useful photocurable compositions comprise one ormore UV-curable components at least one of which is an acid-catalyzedphotocurable component. Such photocurable compositions can furthercomprise a photoacid generator that participates in the generation ofacid radicals that cause photocuring of photocurable components.

Some useful acid-catalyzed photocurable components are photocurableepoxy materials. Cationically photocurable epoxy materials can beorganic compounds having at least one oxirane ring, which oxirane ringis shown in the following formula:

that is polymerizable (photocurable) by a ring opening mechanism. Suchepoxy materials include monomeric epoxy compounds and epoxides of thepolymeric type and can be aliphatic, cycloaliphatic, aromatic orheterocyclic. These materials generally have, on the average, at leastone polymerizable epoxy group per molecule, or typically at least about1.5 or even at least about 2 polymerizable epoxy groups per molecule.Polymeric epoxy materials include linear polymers having terminal epoxygroups (for example, a diglycidyl ether of a polyoxyalkylene glycol),polymers having skeletal (backbone) oxirane units (for example,polybutadiene polyepoxide), and polymers having pendant epoxy groups(for example, a glycidyl methacrylate polymer or copolymer). Thephotocurable epoxy materials can be single compounds or they can bemixtures of different epoxy materials containing one, two, or more epoxygroups per molecule.

The epoxy materials can vary from low molecular weight monomericmaterials to high molecular weight polymers and they can vary greatly inthe nature of the backbone and substituent (or pendant) groups. Forexample, the backbone can be of any type and substituent groups thereoncan be any group that does not substantially interfere with cationicphotocuring process desired at room temperature. Illustrative ofpermissible substituent groups include but are not limited to, halogens,ester groups, ethers, sulfonate groups, siloxane groups, nitro groups,and phosphate groups.

Useful epoxy materials include those that contain cyclohexene oxidegroups such as epoxycyclohexane carboxylates, such as3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate,3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexanecarboxylate, and bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate. A moredetailed list of useful epoxy materials of this nature is provided inU.S. Pat. No. 3,117,099 (Proops et al.).

Still other useful epoxy materials include glycidyl ether monomers thatare glycidyl ethers of polyhydric phenols obtained by reacting apolyhydric phenol with an excess of a chlorohydrin such asepichlorohydrin [for example, the diglycidyl ether of2,2-bis-(2,3-epoxypropoxyphenol)-propane]. Further examples of epoxymaterials of this type are described in U.S. Pat. No. 3,018,262(Schroeder) and in “Handbook of Epoxy Resins” by Lee and Neville,McGraw-Hill Book Co., New York (1967).

Still other useful epoxy materials are resins such as copolymers derivedfrom acrylic acid esters reacted with glycidol such as glycidyl acrylateand glycidyl methacrylate, copolymerized with one or more ethylenicallyunsaturated polymerizable monomers. Other useful epoxy materials areepichlorohydrins, alkylene oxides such as propylene oxide and styreneoxide, alkenyl oxides such as butadiene oxide, and glycidyl esters suchas ethyl glycidate. Still other useful epoxy materials are siliconeshaving an epoxy functionality or group such as cyclohexylepoxy groups,especially those epoxy materials having a silicone backbone. Commercialexamples of such epoxy materials include UV 9300, UV 9315, UV 9400, UV9425 silicone materials that are available from Momentive.

Polymeric epoxy materials can optionally contain other functionalitiesthat do not substantially interfere with cationic photocuring of thephotocurable composition at room temperature. For example, thephotopolymerizable epoxy materials can also include free-radicallypolymerizable functionality.

The photopolymerizable epoxy material can comprise a blend or mixture oftwo or more different epoxy materials. Examples of such blends includetwo or more molecular weight distributions of photopolymerizable epoxymaterials, such as a blend of one or more low molecular weight (below200) epoxy materials with one or more intermediate molecular weight(from 200 to 10,000) photopolymerizable epoxy materials, or one or moreof such photopolymerizable epoxy materials with one or more highermolecular weight (above about 10,000) epoxy materials. Alternatively oradditionally, the photopolymerizable epoxy material can comprise a blendof epoxy materials having different chemical natures, such as aliphaticand aromatic natures, or different functionalities, such as polar andnon-polar properties.

One or more photocurable epoxy materials are included in thephotocurable composition in a suitable amount to provide the desiredefficient photocuring (or photopolymerization). For example, the one ormore photopolymerizable epoxy materials can be present in an amount ofat least 5 weight % and up to and including 50 weight %, or typically ofat least 10 weight % and up to and including 40 weight %, based on thetotal weight of the photocurable composition.

Various compounds can be used as photoacid generators to generate asuitable acid to participate in the photocuring of the epoxy materials.Some of these “photoacid generators” are acidic in nature and others arenonionic in nature. Other useful photoacid generators besides thosedescribed below would be readily apparent to one skilled in the art inview of the teaching provided herein.

Onium salt acid generators useful in the practice of this invention asphotoacid generators include but are not limited to, salts of diazonium,phosphonium, iodonium, or sulfonium salts including polyaryl diazonium,phosphonium, iodonium, and sulfonium salts. The iodonium or sulfoniumsalts include but not limited to, diaryliodonium and triarylsulfoniumsalts. Useful counter anions include but are not limited to complexmetal halides, such as tetrafluoroborate, hexafluoroantimonate,trifluoromethanesulfonate, hexafluoro-arsenate, hexafluorophosphate, andarenesulfonate. The onium salts can also be oligomeric or polymericcompounds having multiple onium salt moieties as well as moleculeshaving a single onium salt moiety.

Suitable iodonium salts include compounds are described in U.S. Pat. No.5,545,676 (Palazzotto et al.) at column 2 (lines 28 through 46), as wellas in U.S. Pat. No. 3,729,313 (Smith), U.S. Pat. No. 3,741,769 (Smith),U.S. Pat. No. 3,808,006 (Smith), U.S. Pat. No. 4,250,053 (Smith), andU.S. Pat. No. 4,394,403 (Smith).

Useful iodonium salts can be simple salts (for example, containing ananion such as chloride, bromide, iodide, or C₄H₅SO₃ ⁻) or a metalcomplex salt (for example, containing SbF₆ ⁻, PF₆ ⁻,tetrakis(perfluorophenyl)borate, or SbF₅OH₃₁AsF₆ ⁻). Mixtures of any ofthese iodonium salts of the same or different class can be used ifdesired. Sulfonium salts are desirable for use and should be soluble inany inert organic solvents (described below) and they should also beshelf-stable, meaning they do not spontaneously promote polymerizationwhen mixed with the other components especially an electron acceptorphotosensitizes and an electron donor co-initiator prior to exposure tosuitable radiation. Particularly useful sulfonium salts include but arenot limited to, triaryl-substituted salts such as mixed triarylsulfoniumhexafluoroantimonates (for example, commercially available as UVI-6974from Dow Chemical Company), mixed triarylsulfonium hexafluorophosphates(for example, commercially available as UVI-6990 from Dow ChemicalCompany), and arylsulfonium hexafluorophosphates (for example,commercially available from Sartomer Company).

One or more onium salts (such as an iodonium salt or a sulfonium salt)can be generally present in the photocurable composition in an amount ofat least 0.05 weight % and up to and including 10 weight %, or typicallyat least 0.1 weight % and up to and including 10 weight %, or even atleast 0.5 weight % and up to and including 5 weight %, based on thetotal weight of the photocurable composition.

Nonionic photoacid generators are also useful in present invention,which compounds include but are not limited to, diazomethane derivativessuch as, for example, bis(benzenesulfonyl)diazomethane,bis(p-toluenesulfonyl)-diazomethane, bis(xylenesulfonyl)diazomethane,bis(cyclohexylsulfonyl)-diazomethane,bis(cyclopentylsulfonyl)diazomethane, bis(n-butylsulfonyl)diazomethane,bis(iso-butylsulfonyl)diazomethane, bis(sec-butylsulfonyl)-diazomethane,bis(n-propylsulfonyl)diazomethane, bis(iso-propylsulfonyl)-diazomethane,bis(tert-butylsulfonyl)diazomethane, bis(n-amylsulfonyl)-diazomethane,bis(isoamylsulfonyl)diazomethane, bis(sec-amylsulfonyl)-diazomethane,bis(tert-amylsulfonyl)diazomethane, 1-cyclohexylsulfonyl-1-(tert-butylsulfonyl)diazomethane,1-cyclohexylsulfonyl-1-(tert-amylsulfonyl)-diazomethane, and1-tert-amylsulfonyl-1-(tert-butyl sulfonyl)diazomethane. Nonionicphotoacid generators can also include glyoxime derivatives. Usefulphotoacid generators can also include bissulfone derivatives. Otherclasses of useful nonionic photoacid generators include disulfonoderivatives.

One or more nonionic photoacid generators can be present in thephotocurable composition in an amount of at least 0.05 weight % and upto and including 10 weight %, or typically at least 0.1 weight % and upto and including 10 weight %, or even at least 0.5 weight % and up toand including 5 weight %, based on the total weight of the photocurablecomposition.

Some photocurable compositions described herein, especially thosecontaining photopolymerizable epoxy materials and photoacid generators,can contain one or more electron donor photosensitizers to improvephotocuring efficiency. Useful electron donor photosensitizers should besoluble in the photocurable composition, free of functionalities thatwould substantially interfere with the cationic photocuring process, andcapable of light absorption (sensitivity) within the range ofwavelengths of at least 150 nm and up to and including 1000 nm.

Suitable electron donor photosensitizers initiate the chemicaltransformation of an onium salt (or other photoacid generator) inresponse to the photons absorbed from the irradiation. The electrondonor photosensitizer should also be capable of reducing the photoacidgenerator after the electron donor photosensitizer has absorbed light(that is, photoinduced electron transfer). Thus, the electron donorphotosensitizer, upon absorption of photons from irradiation, isgenerally capable of donating an electron to the photoacid generator.

When very rapid curing (such as the curing of thin applied films of thephotocurable compositions) is desired, the electron donorphotosensitizers can have an extinction coefficient of at least 1000liter-mole⁻¹ cm⁻¹ and typically at least 50,000 liters-mole⁻¹ cm⁻¹ atthe desired irradiation wavelength using the photocuring process. Forexample, each of the electron donor photosensitizers generally has anoxidation potential of at least 0.4 V and up to and including 3 V vs.SCE.

In general, many different classes of compounds can be used as electrondonor photosensitizers for various reactants. Useful electron donorphotosensitizers include but are not limited to, aromatics such asnaphthalene, 1-methylnaphthalene, anthracene, 9,10-dimethoxyantliracene,benz[a]anthracene, pyrene, phenanthrene, benzo[c]phenanthrene, andfluoranthene. Other useful electron donor photosensitizers that involvethe triplet excited state are carbonyl compounds such as thioxanthonesand xanthones. Ketones including aromatic ketones such as fluorenone,and coumarin dyes such as ketocoumarins such as those with strongelectron donating moieties (such as dialkylamino) can also be used aselectron donor photosensitizers. Other suitable electron donorphotosensitizers are believed to include xanthene dyes, acridine dyes,thiazole dyes, thiazine dyes, oxazine dyes, azine dyes, aminoketonedyes, porphyrins, aromatic polycyclic hydrocarbons, p-substitutedaminostyryl ketone compounds, aminotriarylmethanes, merocyanines,squarylium dyes, and pyridinium dyes.

It is also possible to use a mixture of electron donor photosensitizersthat are chosen from the same or different classes of materials.

The one or more electron donor photosensitizers can be present in thephotocurable composition in an amount of at least 0.000001 weight % andup to and including 5 weight %, and typically at least 0.0001 weight %and up to and including 2 weight %, based on the total weight of thephotocurable composition.

In some embodiments, the electron donor photosensitizer is a pyrene,benzopyrene, perylene, or benzoperylene that is present in an amount ofat least 0.0001 weight % and up to and including 2 weight %, based onthe total weight of the photocurable composition.

In other embodiments, the electron donor photosensitizer can be replacedwith a combination of one or more electron acceptor photosensitizers andone or more electron donor co-initiators.

Useful electron acceptor photosensitizers should be soluble in thephotocurable composition, free of functionalities that wouldsubstantially interfere with the cationic photocuring process, andcapable of light absorption (sensitivity) within the range ofwavelengths of at least 150 nm and up to and including 1000 nm.

Suitable electron acceptor photosensitizers initiate the chemicaltransformation of an onium salt in response to the photons absorbed fromthe irradiation. The electron acceptor photosensitizer should also becapable of oxidizing the electron donor co-initiator (described below)to a radical cation after the electron acceptor photosensitizer hasabsorbed light (that is, photoinduced electron transfer). Thus, theelectron acceptor photosensitizer, upon absorption of photons fromirradiation, is generally capable of accepting an electron from theelectron donor co-initiator.

When very rapid curing (such as the curing of thin applied films of thecompositions) is desired, the electron acceptor photosensitizers canhave an extinction coefficient of at least 1000 liter-mole⁻¹ cm⁻¹ andtypically at least 10,000 liters-mole⁻¹ cm⁻¹ at the desired irradiationwavelength using the photocuring process.

In general, many different classes of compounds can be used as electronacceptor photosensitizers for various reactants, provided that theenergetic requirements discussed above are satisfied. Useful electronacceptor photosensitizers include but are not limited to, cyanoaromaticssuch as 1-cyanonaphthalene, 1,4-dicyanonaphthalene,9,10-dicyanoanthracene, 2,9,10-tricyanoanthracene,2,6,9,10-tetracyanoanthracene; aromatic anhydrides and imides such as1,8-naphthylene dicarboxylic, 1,4,6,8-naphthalene tetracarboxylic,3,4-perylene dicarboxylic, and 3,4,9,10-perylene tetracarboxylicanhydride or imide; condensed pyridinium salts such as quinolinium,isoquinolinium, phenanthridinium, acridinium, and pyrylium salts. Otheruseful electron acceptor photosensitizers that involve the tripletexcited state are carbonyl compounds such as quinones such as benzo-,naphtho-, anthro-quinones having electron withdrawing substituents (suchas chloro and cyano). Ketones including aromatic ketones such asfluorenone, and coumarin dyes such as ketocoumarins such as those withstrong electron withdrawing moieties (such as pyridinium) can also beused as electron acceptor photosensitizers. Other suitable electronacceptor photosensitizers are believed to include xanthene dyes,acridine dyes, thiazole dyes, thiazine dyes, oxazine dyes, azine dyes,aminoketone dyes, porphyrins, aromatic polycyclic hydrocarbons,p-substituted aminostyryl ketone compounds, aminotriaryl methanes,merocyanines, squarylium dyes and pyridinium dyes. Diarylketones andother aromatic ketones such as fluorenone are useful electron acceptorphotosensitizers.

The one or more electron acceptor photosensitizers can be present in thephotocurable composition in an amount of at least 0.000001 weight % andup to and including 5 weight %, and typically at least 0.0001 weight %and up to and including 2 weight %, based on the total weight of thephotocurable composition.

The use of the electron acceptor photosensitizers is highly effective bythe inclusion of one or more electron donor co-initiators in thephotocurable composition, each of which electron donor co-initiators hasan oxidation potential of at least 0.1 V and up to and including 3 V vs.SCE. Such electron donor co-initiators should be soluble in thephotocurable composition.

Useful electron donor co-initiators are alkyl aromatic polyethers,arylalkylamino compounds wherein the aryl group is substituted by one ormore electron withdrawing groups including but not limited to,carboxylic acid, carboxylic acid esters, ketones, aldehydes, sulfonicacid, sulfonates, and nitrile groups. For example, aryl dialkyldiaminocompounds are useful in which the aryl is a substituted or unsubstitutedphenyl or naphthyl group (such a phenyl or naphthyl group with one ormore electron withdrawing groups as noted above), and the two alkylgroups independently comprise 1 to 6 carbon atoms.

In general, the one or more electron donor co-initiators can be presentin an amount at least 0.001 weight % and up to and including 10 weight%, or more typically of at least 0.005 weight % and up to and including5 weight %, or even at least 0.01 weight percent and up to and including2 weight %, based on the total weight of the photocurable composition.

As noted above, all of the photocurable compositions containing variousessential and optional components can further comprise dispersed carbonblack in an amount of at least 0.5 weight % and up to and including 20weight %, or at least 1 weight % and up to and including 10 weight %,based on the total weight of the photocurable composition.

Some embodiments of photocurable compositions useful in the presentinvention can comprise each of a photopolymerizable epoxy material asdescribed above, a photoacid generator as described above, an electrondonor photosensitizer as described above, dispersed metal particles asdescribed below, an organic diluent such as an organic solvent medium asdescribed below, a free-radically polymerizable material as describedabove, and a free radical photoinitiator as described above, wherein:

the photopolymerizable epoxy material has at least two polymerizableepoxy groups per molecule,

the photoacid generator is an iodonium or sulfonium, and

the metal particles are dispersed carbon-coated silver particles ordispersed carbon-coated copper particles (described below) that have amedian diameter equal to or less than 0.5 μm as determined using adynamic light scattering method.

Free Radical Photocurable Chemistries:

In other embodiments, the photocurable compositions can comprise one ormore UV-curable components at least one of which is a free radicallyphotocurable component and the photocurable composition can furthercomprise a free radical photoinitiator to provide free radicals duringphotocuring.

The one or more free-radically polymerizable compounds can be present toprovide free-radically polymerizable functionality, includingethylenically unsaturated polymerizable monomers, oligomers, or polymerssuch as mono-functional or multi-functional acrylates (also includesmethacrylates). Such free-radically polymerizable compounds comprise atleast one ethylenically unsaturated polymerizable bond (moiety) and theycan comprise two or more of these unsaturated moieties in manyembodiments. Suitable materials of this type contain at least oneethylenically unsaturated polymerizable bond and are capable ofundergoing addition (or free radical) polymerization. Such freeradically polymerizable materials include mono-, di-, or poly-acrylatesand methacrylates including but not limited to, methyl acrylate, methylmethacrylate, ethyl acrylate, isopropyl methacrylate, n-hexyl acrylate,stearyl acrylate, allyl acrylate, glycerol diacrylate, glyceroltriacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate,triethylene glycol dimethacrylate, 1,3-propanediol diacrylate,1,3-propanediol dimethacrylate, 1, 4-butanediol diacrylate,1,6-hexanediol diacrylate, neopentyl glycol diacrylate, neopentyl glycoldimethacrylate, trimethylolpropane triacrylate, 1,2,4-butanetrioltrimethacrylate, 1,4-cyclohexanediol diacrylate, pentaerythritoltriacrylate, pentaerythritol tetraacrylate, pentaerythritoltetramethacrylate, dipentaetrythritol hexaacrylate, sorbitolhexaacrylate, bis[1-(2-acryloxy)]-p-ethoxyphenyldimethylmethane,bis[1-(3-acryloxy-2-hydroxy)]-p-propoxyphenyldimethylmethane, andtris-hydroxyethyl-isocyanurate trimethacrylate; the bis-acrylates andbis-methacrylates of polyethylene glycols having a molecular weight offrom 200 to and including 500, co-polymerizable mixtures of acrylatemonomers such as those described in U.S. Pat. No. 4,652,274 (Boettcheret al.) and acrylate oligomers such as those described in U.S. Pat. No.4,642,126 (Zader et al.); and vinyl compounds such as styrene andstyrene derivatives, diallyl phthalate, divinyl succinate, divinyladipate, and divinyl phthalate.

Although the amount of the one or more free radically polymerizablematerials is not particularly limited, they can be present in thephotocurable compositions in an amount of at least 30 weight % and up toand including 90 weight % or typically of at least 40 weight % and up toand including 85 weight %, based on the total weight of the photocurablecomposition.

One or more free radical photoinitiators can also be present in thephotocurable compositions to generate free radicals. Such free radicalphotoinitiators include any compound that is capable of generating freeradicals upon exposure to photocuring radiation such as ultraviolet orvisible radiation. For example, free radical photoinitiators can beselected from triazine compounds, thioxantone compounds, benzoincompounds, carbazole compounds, diketone compounds, sulfonium boratecompounds, diazo compounds, benzophenone compounds, and biimidazolecompounds, and others that would be readily apparent to one skilled inthe art.

One or more free radical photoinitiators can be present in thephotocurable composition in an amount of at least 0.3 weight % and up toand including 10 weight %, or typically at least 0.4 weight % and up toand including 10 weight %, or even at least 0.5 weight % and up to andincluding 5 weight %, based on the total weight of the photocurablecomposition.

In some of these embodiments, the photocurable composition comprises oneor more free-radically polymerizable materials as described above, oneor more free radical photoinitiators as described above, dispersed metalparticles such as dispersed carbon-coated silver particles as describedbelow, an organic solvent medium (as described below), wherein anacrylate is present as one of the free radically polymerizablecomponents.

The photocurable compositions described herein, of either acid catalyzedchemistry or free radical chemistry generally include suitable metalparticles that can act as seed metal catalytic sites for electrolessplating processes. Usually only one type of metal particles are used,but it is also possible to include mixtures of metal particles, from thesame or different classes of metals, that do not interfere with eachother. These metal particles generally have a net neutral charge.

Useful metal particles can be chosen from one or more classes of noblemetals, semi-noble metals, Group IV metals, or combinations thereof.Useful metal particles include but are not limited to, particles ofgold, silver, palladium, platinum, rhodium, iridium, rhenium, mercury,ruthenium, osmium, iron, cobalt, nickel, copper, aluminum, zinc, andtungsten. Useful particles of Group IV metals include but are notlimited to particles of tin, titanium, and germanium. The noble metalparticles such as particles of silver, palladium, and platinum areparticularly useful, and the semi-noble particles of nickel and copperare also particularly useful. Tin particles are particularly useful inthe Group IV metal class. In many embodiments, silver particles orcopper particles are used in the photocurable composition.

The metal particles useful in the present invention can be coated andisolated from each other using surfactants, polymers, or carbon. Thecarbon on carbon-coated metal particles can be amorphous, sp2hybridized, or graphene-like in nature. Such carbon can be used toprevent aggregation of metal particles and provide improveddispersibility in the photopolymerizable composition. Usefulcarbon-coated metal particles include carbon-coated silver particles andcarbon-coated copper particles, or mixtures of carbon-coated silverparticles and carbon-coated copper particles.

The metal particles useful in the photocurable compositions can bedispersed in various organic solvents and can have improveddispersibility in the presence of the other components of thephotocurable composition, such as multifunctional polymeric epoxymaterials or in the presence of optional components such asmultifunctional acrylate resins described below. Useful dispersants areknown in the art and can also be present if desired. The methods used todisperse the metal particles include but are not limited to,ball-milling, magnetic stirring, high speed homogenization, highpressure homogenization, and ultrasonication.

The metal particles useful in these embodiments can be present in thephotocurable compositions as individual particles, but in manyembodiments, the metal particles are present as agglomerations of two ormore metal particles. Such metal particles can be present in anygeometric shape including but not limited to, spheres, rods, prisms,cubes, cones, pyramids, wires, flakes, platelets, and combinationsthereof, and they can be uniform or non-uniform in shapes and sizes. Theaverage particle size of individual and agglomerated metal particles canvary from at least 0.01 μm and up to and including 25 μm, or more likelyof at least 0.02 μm and up to and including 5 p.m. Although the size ofthe metal particles is not particularly limited, optimal benefits can beachieved using metal particles as individual particles or agglomerates,having an average particle size of at least 0.02 μm and up to andincluding 10 μm. The particle size distribution is desirably narrow asdefined as one in which greater than 50%, or typically at least 75%, ofthe particles have a particle size in the range of 0.2 to 2 times theaverage particle size. The average particle size (same as mean particlesize) can be determined from the particle size distribution that can bedetermined using any suitable procedure and equipment including thatavailable from Coulter or Horiba and the appropriate mathematicalcalculations used with that equipment.

When carbon-coated metal particles are used, they can be designed tohave a median particle diameter that is equal to or less than 0.6 μm, orless than 0.2 μm, or more likely less than 0.1 μm. Such carbon-coatedmetal particles generally have a minimum median diameter of 0.005 Medianparticle diameter [Dv (50%)] can be determined using a dynamic lightscattering method. For example, such a method can be carried out using aMalvern Zetasizer Nano ZS that can be obtained commercially from MalvernInstruments, Ltd.

The photocurable compositions are generally provided in a suitableorganic diluent that serves as a non-aqueous (organic) solvent orcombination of solvents in which the components of the photocurablecomposition are dissolved or dispersed. In many embodiments, the organicdiluent is an organic solvent medium that includes one or more inertorganic solvents such as 2-ethoxyethanol, 2-(2-methoxyethoxy)ethanol,2-(2-ethoxyethoxy)ethanol, 1-methoxy-2-propanol (DOWANOL™ PM organicsolvent), 4-heptanone, 3-heptanone, 2-heptanone, cyclopentanone,cyclohexanone, diethyl carbonate, 2-ethoxyethyl acetate, N-butylbutyrate, acetone, dichloromethane, isopropanol, ethylene glycol, andmethyl lactate. Mixtures of these listed inert organic solvents can beused in the organic solvent medium in any suitable volume or weightratio. Other useful organic solvents could be readily identified by oneskilled in the art using the teaching provided herein. By “inert”, it ismeant that the organic solvents do not appreciably participate in anychemical reactions.

The organic diluent (such as the organic solvent medium) can provide upto and including 1 weight %, or up to at least 70 weight % or at least10 weight % and up to and including 30 weight %, based on the totalweight of the photocurable composition. The amount of inert organicsolvents can be judiciously chosen depending upon the particularmaterials used, the means for applying the resulting photocurablecomposition, and desired properties including composition uniformity.The organic diluent typically includes little or no water (generallyless than 5 weight % of the total photocurable composition weight) sothat the photocurable compositions are considered “photocurablecompositions”.

When one or more photocurable components (as described above) arepresent as liquid organic compounds, those one or more photocurablecomponents can act as the organic diluent and separate inert organicsolvents may not be necessary. In such instances, the organic diluentcan be considered a “reactive” diluent. Alternatively, one or morereactive diluents can be used combination with one or more inert organicsolvents to form a suitable organic diluent.

While not essential to the photocurable compositions, an optional butdesirable component is carbon black in an amount of at least 0.5 weight% and up to and including 20 weight %, or at typically at least 1 weight% and up to and including 10 weight %, based on the total weight of thephotocurable composition.

Articles

The photocurable compositions described above can be formulated asdescribed above and applied to one or both supporting sides (planarsides) of any suitable substrate (described below) using any suitablemanner to form a “precursor article”. For example, the photocurablecomposition can be applied in a uniform or pattern-wise manner to eitheror both supporting sides using for example dip coating, roll coating,hopper coating, spray coating, spin coating, ink jetting,photolithographic imprinting, flexographic printing using flexographicprinting members (such as flexographic printing plates and flexographicprinting sleeves), lithographic printing using lithographic printingplates, and gravure or intaglio printing using appropriate printingmembers. Flexographic printing using flexographic printing members isparticularly useful to provide predetermined patterns of thephotocurable composition, and this method can be used to providemultiple patterns of the same or different photocurable compositions onone or both supporting sides of the substrate, and in one or multipleportions of either supporting side of the substrate such as when it is acontinuous polymeric web. More details of such processes are providedbelow.

The applied photocurable composition can be formed and dried into auniform layer or a dried into a predetermined pattern. The resultingarticles can be considered “precursor” articles before photocuring iscarried out as described below.

As noted below in more detail, the substrates for such articles can becomposed of any useful material(s) and can be individual films or sheetsof any suitable sizes and shapes for example composed of a metallicmaterial, glass, paperstock (any type of cellulosic material) orceramic, or they can be continuous webs of materials such as continuouspolymeric webs such as continuous poly(ethylene terephthalate) webs.

The various amounts of essential and optional components of thephotocurable compositions are described above but are to be understoodthat they refer to solutions or dispersions containing such components.However, it should be understood that upon application to a suitablesubstrate, and optional drying, and then photocuring, the amounts ofvarious components can be different within the applied photocurablecomposition. The individual amounts and relative amounts of theremaining components (if for example, inert organic solvents have beenremoved) can be readily calculated from the information of the amountsof components within the photocurable composition before application toa substrate.

For example, in the dried photocurable compositions, the metal particles(such as carbon-coated metal particles) can be present in an amount ofat least 10 weight % and up to and including 90 weight %, particledispersing agent(s) can be present in an amount of at least 1 weight %and up to and including 30 weight %, individual carbon particles can bepresent in an amount of up to and including 20 weight %, andphotocurable components (described above, before curing) can be presentin amounts of up to and including 90 weight %.

Once the photocurable compositions are applied onto one or bothsupporting sides to a transparent substrate in a suitable manner, forexample in a patternwise fashion, the resulting an intermediate articlethat can be treated in a suitable manner to photocure the photocurablecompositions in suitable patterns to provide electrically-conductivepatterns having seed metal catalysts. Electrically-conductive metalpatterns can then be formed in a suitable manner as described in moredetail below using electroless plating processes.

A suitable dry outermost polymeric coating can be disposed over theentire surface of each electrically-conductive metal pattern but in mostembodiments, it is disposed only over part of theelectrically-conductive metal pattern. For example, it can be disposedover the entire electrically-conductive metal grid but only over part ofthe electrically-conductive metal connector, using a non-crosslinkedthermoplastic polymer as described above. This arrangement of the dryoutermost polymeric layer can be disposed on only one of the firstsupporting side and the opposing second supporting side, or on both ofthese supporting sides.

The dry outermost polymeric coating can have a dry thickness of lessthan 5 μm or more likely less than 3 μm or even less than 1 μm. Themaximum dry thickness is not limited but for practical purposes, themaximum dry thickness is at most 20 μm. The dry outermost polymericcoating also has an integrated transmittance of at least 80% or morelikely at least 90% as measured using techniques described above, and aglass transition temperature of at least 65° C. as described above. Insome embodiments, the dry outermost polymeric coating has both a drythickness of less than 3 μm and an integrated transmittance of greaterthan 90%, and the non-crosslinked thermoplastic polymer is anon-crosslinked thermoplastic non-aromatic polymer that is anon-crosslinked thermoplastic acrylic polymer.

In some particularly useful embodiments, such articles compriseelectrically-conductive patterns (such as electrically-conductive metalpatterns) on either or both of the first supporting side and theopposing second supporting side on a transparent substrate, whichcomprise electrically-conductive metal patterns, for example arecomposed of metal wires, which are composed of silver, copper,palladium, or platinum, and particularly copper or silver. In addition,such electrically-conductive metal patterns can be obtained byelectrolessly plating carbon-coated metal particles such ascarbon-coated silver particles, and optionally individual carbonparticles mixed with the carbon-coated metal particles. Where theelectrically-conductive metal patterns have both electrically-conductivemetal grids and electrically-conductive metal connectors, theelectrically-conductive metal connectors can be similarly composedexcept that they may comprise substantially no individual carbonparticles (meaning that there are less than 5 weight % individual carbonparticles).

Thus, once the intermediate articles are subjected to conditions forphotocuring the photocurable compositions disposed on the supportingside(s) of a transparent substrate, and the dry outermost polymericcoatings are formed using procedures and equipment described below, theresulting product articles can be incorporated into touch screens orother devices where electrically-conductive patterns are needed.

Use of Photocurable Compositions

Before provision of the dry outermost polymeric coatings, thephotocurable compositions described herein can be photocured (orphotopolymerized) using suitable radiation including ultraviolet lightor visible actinic light, or both. One or more suitable light sourcescan be used for the exposure process. Each precursor article can beexposed individually as a single element, or in alternative embodimentsdescribed below, a continuous web (for example, a roll-to-rollcontinuous polymeric web) comprising multiple precursor articles(comprising multiple photocurable patterns) in multiple portions on oneor both supporting sides of the continuous polymeric web can be exposedindividually or collectively as the continuous polymeric web is passedthrough exposure stations, or as an exposure device is passed in adesired path over the continuous polymeric web. The same or differentphotocurable compositions can be applied (for example, printed usingflexography and flexographic printing members) on both supporting sidesof the substrate whether the substrate is in the form of a singleelement or continuous polymeric web. In many embodiments, differentelectrically-conductive patterns can be formed on opposing supportingsides of the substrate (or continuous polymeric web) using thephotocurable compositions described herein.

When a photocurable composition is uniformly applied to a suitablesubstrate, the resulting uniform dried layer can be “imaged” orselectively exposed (or patterned) with exposing radiation through asuitable photomask (masking element) having a desired pattern, and thenappropriately removing the non-crosslinked (non-cured) photocurablecomposition using a suitable “developer” solution that solubilizes orotherwise removes the non-photocured material. These features or stepscan be carried out on both (opposing) supporting sides of the substrate.Multiple electrically-conductive and photocured patterns can be formedin the dried layer if desired using the same or different photomasks.

More likely, predetermined patterns of one or more photocurablecompositions can be formed on a suitable substrate using methods asdescribed below.

Suitable substrates (also known as “receiver elements” in the art)useful to provide precursor articles can be composed of any suitablematerial as long as it does not inhibit the purpose of the photocurablecomposition. For example, useful substrates can be formed from materialsincluding but are not limited to, polymeric films, metals, paperstock,rigid or flexible glasses (untreated or treated for example withtetrafluorocarbon plasma, hydrophobic fluorine, or a siloxanewater-repellant material), silicon or ceramic wafers, fabrics, andcombinations thereof (such as laminates of various films, or laminatesof papers and films) provided that a uniform layer or pattern of aphotocurable composition can be formed thereon in a suitable manner andfollowed by irradiation to form a uniform photocured layer or one ormore photocured patterns on at least one receptive (supporting) surfacethereof. The substrate can be transparent, translucent, or opaque, andrigid or flexible. Many useful substrates are transparent and have anintegrated transmittance of at least 90%, and such transparentsubstrates can also be flexible continuous polymeric webs.

The substrate can include one or more auxiliary polymeric ornon-polymeric layers or one or more patterns of other materials that areapplied before a photocurable composition is applied. For example,either or both supporting (planar) surfaces of the substrate can betreated for example with a primer layer or electrical or mechanicaltreatments (such as graining) to render that surface a “receptivesurface” to improve adhesion of the photocurable composition andresulting photocured layer or photocured pattern. An adhesive layer canbe disposed on the substrate to provide various properties in responseto stimuli (for example, it can be thermally activated, solventactivated, or chemically activated) and that adhesive layer can serve asa receptive layer.

In some embodiments, the substrate can comprise a separate receptivelayer as a receptive surface disposed on a substrate, which receptivelayer and substrate can be composed of a material such as a suitablepolymeric material that is highly receptive of the photocurablecomposition. Such receptive layers can have a dry thickness of at least0.05 μm and up to and including 10 μm, or typically of at least 0.05 μmand up to and including 3 μm, when measured at 25° C.

Either supporting side of the substrate (especially polymericsubstrates) can be treated by exposure to corona discharge, mechanicalabrasion, flame treatments, or oxygen plasmas, or by coating withvarious polymeric films, such as poly(vinylidene chloride) or anaromatic polysiloxane as described for example in U.S. Pat. No.5,492,730 (Balaba et al.) and U.S. Pat. No. 5,527,562 (Balaba et al.)and U.S. Patent Application Publication 2009/0076217 (Gommans et al.).

More particularly, suitable substrate materials for forming precursorarticles as continuous webs include but are not limited to, metallicfilms or foils, metallic films on polymer (such as metallic films onelectrically-conductive polymeric films), flexible glasses,semi-conducting organic or inorganic films, organic or inorganicdielectric films, or laminates of two or more layers of such materials.For example, useful continuous web substrates can include polymericfilms such as poly(ethylene terephthalate) films, poly(ethylenenaphthalate) films, polyimide films, polycarbonate films, polyacrylatefilms, polystyrene films, polyolefin films, and polyimide films, metalfoils such as aluminum foils, cellulosic papers or resin-coated orglass-coated papers, cardboard webs, and metalized polymeric films.

Particularly useful substrates are transparent polyesters films composedof poly(ethylene terephthalate) or poly(ethylene naphthalate), and filmsof polycarbonate, or poly(vinylidene chloride) with or withoutsurface-treatments as noted above, all have the integrated transmittancegreater than 90% as described above.

In some embodiments, a first polymer latex and second polymer latex canbe mixed to form a dried primer layer on a substrate to adhere patternedmaterials having fine electrically-conductive lines formed using thephotocurable composition. The first polymer latex can comprise a firstpolymer and a first surfactant such that a dried coating of the firstpolymer latex has a surface polarity of at least 50%. The second polymerlatex can comprise a second polymer and a second surfactant such that adried coating of the second polymer latex has a surface polarity of lessthan or equal to 27%.

At least one of the first and second polymers described herein comprisesa vinyl polymer comprising recurring units derived at least in part fromglycidyl (meth)acrylate (meaning glycidyl acrylate, glycidylmethacrylate, or both). In addition, at least one of the first polymerand second polymer is crosslinkable, which polymer can be crosslinkedfor example after coating the polymer mixture onto a suitable supportsuch as during drying or various heat treatments of the substrate.

The first polymer can be a homopolymer derived from glycidyl(meth)acrylate but more likely it is a copolymer derived from glycidyl(meth)acrylate and one or more other ethylenically unsaturatedpolymerizable monomers.

The first polymer is particularly designed by co-polymerizing one ormore glycidyl (meth)acrylates with one or more alkyl (meth)acrylateswherein the ester alkyl group has at least 2 carbon atoms including butnot limited to, ethyl acrylate, ethyl methacrylate, n-butyl acrylate,n-butyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate,lauryl acrylate, lauryl methacrylate, allyl methacrylate, hydroxyethylmethacrylate, hydroxyethyl acrylate, and others that would be readilyapparent to one skilled in the art.

The second polymer latex can comprise one of more second polymers andone or more second surfactants (described below) such that a driedcoating of the second polymer latex has a surface polarity of less thanor equal to 28% or less than or equal to 27%. Particularly useful secondpolymers are vinyl polymers derived at least in part from one or moreglycidyl-functional ethylenically unsaturated polymerizable monomers,such as glycidyl (meth)acrylate, for example glycidyl acrylate andglycidyl methacrylate, as described above for the first polymer. Thus,the second polymer can be a homopolymer derived from glycidyl(meth)acrylate or a copolymer derived from glycidyl (meth)acrylate andone or more other ethylenically unsaturated polymerizable monomers.

The second polymer is particularly designed by co-polymerizing one ormore glycidyl (meth)acrylates with one or more co-monomers such as oneor more alkyl (meth)acrylates wherein the ester alkyl group has at least2 carbon atoms including but not limited to, ethyl acrylate, ethylmethacrylate, n-butyl acrylate, n-butyl methacrylate, cyclohexylacrylate, cyclohexyl methacrylate, lauryl acrylate, lauryl methacrylate,allyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate,and others that would be readily apparent to one skilled in the art.

The first polymer latex comprises one or more first surfactants, each ofwhich is an alkyl sulfonate sodium salt wherein the alkyl group has atleast 10 carbon atoms. For example, the first surfactant can be a sodiumα-olefin (C₁₄-C₁₆) sulfonate, or the first surfactant can be a compoundrepresented by R—CH₂—CH═CH═CH₂—S(═O)₂O⁻Na⁺ wherein R is a C₁₀, C₁₁, orC₁₂ hydrocarbon group, or mixtures of such compounds with different Rgroups that are any of C₁₀ to C₁₂ hydrocarbons groups.

The second polymer latex comprises one or more second surfactants, eachof which is an alkyl phenol sulfate ammonium salt having at least 3ethylene oxide units. For example, the second surfactant can be anammonium salt of a sulfate polyethoxy nonylphenol, or the secondsurfactant can be represented by R′-phenyl-(O—CH₂CH₂)_(n)—S(═O)O₂ ⁻NH₄ ⁺wherein R′ is a C₈ to C₁₂ hydrocarbon group and n is at least 3 and upto and including 10, or more likely n is at least 3 and up to andincluding 6.

Useful substrates can have a desired dry thickness depending upon theeventual use of the article formed therefrom. For example, the substratedry thickness (including all treatments and auxiliary layers) can be atleast 0.001 mm and up to and including 10 mm, and especially fortransparent polymeric films, the substrate dry thickness can be at least0.008 mm and up to and including 0.2 mm.

The substrate used to prepare the articles described herein can beprovided in various forms, such as for example, individual sheets of anysize or shape, and continuous webs such as continuous webs oftransparent polymeric substrates including transparent polyester websthat are suitable for roll-to-roll operations. Such continuous polymericwebs can be divided or formed into individual first, second, andadditional portions that can be used to form the same or differentphotocured electrically-conductive patterns.

After patternwise application of a photocurable composition, anyremaining organic solvents can be removed by evaporation such as adrying or pre-baking procedure that does not adversely affect theremaining components or prematurely cause photocuring. Useful dryingconditions can be as low as room temperature for as little as 5 secondsand up to and including several hours depending upon the manufacturingprocess. In most processes, such as roll-to-roll processes describedbelow, the drying conditions can be at high enough temperatures andsuitable drying equipment to remove at least 90% of all inert organicsolvent(s) within at least 5 seconds. For example, suitable removal ofinert organic solvents can be achieved by using jets of hot air,evaporation at room temperature, or heating in an oven at an elevatedtemperature.

Any applied uniform layer of a photocurable composition can have a drythickness of at least 0.1 μm and up to and including 10 μm, or typicallyat least 0.2 μm and up to and including 1 μm, and the optimal drythickness can be tailored for the intended use of the resulting uniformphotocured layer, which generally has about the same dry thickness as auniform layer of the non-photocured photocurable composition.

Any applied pattern of the photocurable composition can comprise a gridof lines (or a pattern of other shapes including circles, diamonds, orovals, or an irregular network) having an average dry width of at least0.2 μm and up to and including 100 μm, or typically of at least 5 μm andup to and including 10 μm, and the optimal dry width can be tailored forthe intended use of the resulting uniform photocured layer, whichgenerally has photocured and electrically-conductive metal lines havingessentially the same dimensions as the non-photocuredelectrically-conductive metal lines.

Thus, the present invention can be used to provide articles comprising asubstrate and uniform layers or patterns comprised of the photocurablecomposition, wherein such articles can be considered “precursor”articles, meaning that they are generally the first formed articlesbefore photocuring. Upon photocuring the photocurable compositions, theprecursor article becomes an intermediate (photocured) article.

In some embodiments, the same or different photocurable composition canbe applied in a suitable manner on both supporting sides (planarsurfaces) of the substrate to form “duplex” or dual-sided precursorarticles, and each applied photocurable composition can be in the formof the same or different uniform layer or predetermined pattern.

In many embodiments, a pattern of a photocurable composition is appliedon one or both (opposing) supporting sides of the substrate (for exampleas a roll-to-roll continuous web) using any known printing method suchas inkjet printing, gravure printing, or flexographic printing where arelief element such as elastomeric relief elements (flexographicprinting members) derived from flexographic printing plate precursors,many of which are known in the art and some are commercially available,for example as the CYREL® Flexographic Photopolymer Plates from DuPontand the Flexcel SR and NX Flexographic plates and Flexcel DirectFlexographic plates from Eastman Kodak Company.

Particularly useful elastomeric relief elements are derived fromflexographic printing plate precursors and flexographic printing sleeveprecursors, each of which can be appropriately imaged (and processed ifneeded) to provide the relief elements for “printing” or applying asuitable pattern of a photocurable composition.

For example, an elastomeric relief element (for example, flexographicprinting member) having a relief layer comprising an uppermost reliefsurface and an average relief image depth (pattern height) of at least50 μm can be prepared from imagewise exposure of an elastomericphotopolymerizable layer in an elastomeric relief element precursor suchas a flexographic printing member precursor, for example as described inU.S. Pat. No. 7,799,504 (Zwadlo et al.) and U.S. Pat. No. 8,142,987 (Aliet al.) and U.S. Patent Application Publication 2012/0237871 (Zwadlo),the disclosures of which are incorporated herein by reference fordetails of such flexographic printing member precursors. Suchelastomeric photopolymerizable layers can be imaged through a suitablemask image.

In other embodiments, the elastomeric relief element is provided from adirect (or ablation) laser-engravable elastomer relief elementprecursor, with or without integral masks, as described for example inU.S. Pat. No. 5,719,009 (Fan), U.S. Pat. No. 5,798,202 (Cushner et al.),U.S. Pat. No. 5,804,353 (Cushner et al.), U.S. Pat. No. 6,090,529(Gelbart), U.S. Pat. No. 6,159,659 (Gelbart), U.S. Pat. No. 6,511,784(Hiller et al.), U.S. Pat. No. 7,811,744 (Figov), U.S. Pat. No.7,947,426 (Figov et al.), U.S. Pat. No. 8,114,572 (Landry-Coltrain etal.), U.S. Pat. No. 8,153,347 (Veres et al.), U.S. Pat. No. 8,187,793(Regan et al.), and U.S. Patent Application Publications 2002/0136969(Hiller et al.), 2003/0129530 (Leinenback et al.), 2003/0136285 (Telseret al.), 2003/0180636 (Kanga et al.), and 2012/0240802 (Landry-Coltrainet al.), the disclosures of all of which are incorporated herein fordetails of such laser-engravable precursors.

When elastomeric relief elements are used, a photocurable compositioncan be applied in a suitable manner to the uppermost relief surface(raised surface) in the elastomeric relief element. Such application canbe accomplished using suitable means and it is desirable that as littleas possible is coated onto the sides (slopes) or recesses of the reliefdepressions. Anilox roller systems or other roller application systems,especially low volume Anilox rollers, below 2.5 billion cubicmicrometers per square inch (6.35 billion cubic micrometers per squarecentimeter) and associated skive knives can be used. Optimum metering ofthe photocurable composition onto the uppermost relief surface can beachieved by controlling viscosity or thickness, or choosing anappropriate application means. For example, the photocurable compositioncan be formulated to have a viscosity for such applications of at least1 cps (centipoise) and up to and including 5000 cps. The thickness ofthe photocurable composition on the relief image is generally limited toa sufficient amount that can readily be transferred to a substrate butnot too much to flow over the edges of the elastomeric relief element inthe recesses during application.

Thus, the photocurable composition can be fed from an Anilox or otherroller inking system in a measured amount for each printed precursorarticle (either as a uniform layer or pattern). In one embodiment, afirst roller can be used to transfer the photocurable composition froman “ink” pan or a metering system to a meter roller or Anilox roller. Aphotocurable composition is generally metered to a uniform thicknesswhen it is transferred from the Anilox roller to a printing platecylinder. When the substrate as a continuous web is moved through theroll-to-roll handling system from the printing plate cylinder to animpression cylinder, the impression cylinder applies pressure to theprinting plate cylinder that transfers an image of photocurablecomposition from an elastomeric relief element to the substrate.

After the photocurable composition has been applied to the uppermostrelief surface (or raised surface) of the elastomeric relief element, itcan be useful to remove at least 25 weight % of any inert organicsolvent(s) included in the photocurable composition to form a moreviscous deposit on the uppermost relief surface of the relief image.This removal of inert organic solvents can be achieved in any manner,for example using jets of hot air, evaporation at room temperature, orheating in an oven at an elevated temperature, or other means known inthe art.

Once on the substrate, either in a uniform layer or predeterminedpattern of grid lines or other shapes (on one or both supporting sidesof the substrate), the photocurable composition in the precursor articlecan be irradiated with suitable radiation as described above from asuitable source such as a fluorescent lamp or LED to provide aphotocured layer or one or more photocured patterns on the substrate.For example, photocured can be achieved by the use of UV-visibleirradiation having a wavelength (λ_(max)) of at least 190 nm and up toand including 700 nm and at intensity of at least 1,000 microwatts/cm²and up to and including 80,000 microwatts/cm². The irradiation systemused to generate such radiation can consist of one or more ultravioletlamps for example in the form of 1 to 50 discharge lamps, for example,xenon, metallic halide, metallic arc (such as a low, medium or highpressure mercury vapor discharge lamps having the desired operatingpressure from a few millimeters to about 10 atmospheres). The lamps caninclude envelopes capable of transmitting light of a wavelength of atleast 190 nm and up to and including 700 nm or typically at least 240 nmand up to and including 450 nm. The lamp envelope can consist of quartz,such as spectrocil or Pyrex. Typical lamps that can be employed forproviding ultraviolet radiation are, for example, medium pressuremercury arcs, such as the GE H3T7 arc and a Hanovia 450 W arc lamp.Photocuring can be carried out using a combination of various lamps,some of or all of which can operate in an inert atmosphere. When usingUV lamps, the irradiation flux impinging upon the substrate (or appliedlayer or pattern) can be designed to be sufficient to effect sufficientrapid photocuring of the applied photocurable composition within 1 to 20seconds in a continuous manner, for example in a roll-to-roll operation.

An LED irradiation device to be used in for photocuring can have anemission peak wavelength of 350 nm or more. The LED device can includetwo or more types of elements having different emission peak wavelengthsgreater than or equal to 350 nm. A commercial example of an LED devicethat has an emission peak wavelength of 350 nm or more and has anultraviolet light-emitting diode (UV-LED), is NCCU-033 that is availablefrom Nichia Corporation.

The result of such irradiation of a precursor article is an intermediatearticle comprising the substrate (for example, individual sheets or acontinuous web) and having thereon either a photocured layer or one ormore photocured patterns derived from the photocurable composition onone or both supporting sides of the substrate. Each photocured patterngenerally contains “seed” metallic particles that can be electrolesslyplated as described below.

The resulting intermediate articles can be further processed toincorporate an electrically-conductive metal on the uniform photocuredlayer or photocured pattern(s), each of which includes the metalparticles as “seed” materials for further application ofelectrically-conductive metals, for example using electroless metalplating procedures. For example, the electroless “seed” metal particlesas described above can include silver, palladium, or platinum particles,or mixtures thereof, as well as carbon-coated metal particles describedabove, which can be electrolessly plated with silver, copper, platinum,palladium, or other metals as described below.

One useful method of this invention uses multiple flexographic printingplates (for example, prepared as described above) in a stack in aprinting station wherein each stack has its own printing plate cylinderso that each flexographic printing plate is used to print ontoindividual substrates, or the stack of printing plates can be used toprint multiple portions in a continuous transparent polymeric web (onone or both supporting sides). The same or different photocurablecomposition can be “printed” or applied to such a substrate (on same oropposing supporting sides) using the multiple flexographic printingplates.

In other embodiments, a central impression cylinder can be used with asingle impression cylinder mounted on a printing press frame. As thesubstrate (or receiver element) enters the printing press frame, it isbrought into contact with the impression cylinder and the appropriatepattern is printed with the photocurable composition. Alternatively, anin-line flexographic printing process can be utilized in which theprinting stations are arranged in a horizontal line and are driven by acommon line shaft. The printing stations can be coupled to exposurestations, cutting stations, folders, and other post-processingequipment. A skilled worker could readily determine other usefulconfigurations of equipment and stations using information that isavailable in the art. For example, an in-the-round process is describedin WO 2013/063084 (Jin et al.).

Intermediate articles described herein having the described photocuredelectrically-conductive patterns containing metal particles can beimmediately immersed in an aqueous-based electroless metal plating bathor solution, or the intermediate articles (for example as rolled upcontinuous webs) can be stored with just the photocured pattern(s) foruse at a later time.

For example, each intermediate article can be contacted with anelectroless plating metal that is the same as or different from themetal within the metal particles incorporated within the photocuredpattern(s). In most embodiments, however, the electroless plating metalis a different metal from the metal used in the metal particlesdispersed within the photocured pattern(s).

Any metal that will likely electrolessly “plate” on the metal particlescan be used at this point, but in most embodiments, the electrolessplating metal can be for example copper(II), silver(I), gold(IV),palladium(II), platinum(II), nickel(II), chromium(II), and combinationsthereof. Copper(II), silver(I), and nickel(II) are particularly usefulelectroless plating metals for silver, copper, platinum, or palladiumseed metal catalysts. In some embodiments, the resultingelectrically-conductive metal patterns are composed of silver, copper,palladium, or platinum, or a combination thereof, in either the seedmetal catalysts or plated metals, or both.

The one or more electroless plating metals can be present in theaqueous-based electroless plating bath or solution in an amount of atleast 0.01 weight % and up to and including 20 weight % based on totalplating bath or solution weight.

Electroless plating can be carried out using known temperature and timeconditions, as such conditions are well known in various textbooks andscientific literature. It is also known to include various additivessuch as metal complexing agents or stabilizing agents in theaqueous-based electroless plating solutions. Variations in time andtemperature can be used to change the metal electroless platingthickness or the metal electroless plating deposition rate.

A useful aqueous-based electroless plating solution or bath is anelectroless copper(II) plating bath that can contain formaldehyde as areducing agent. Ethylenediaminetetraacetic acid (EDTA) or salts thereofcan be present as a copper complexing agent. For example, copperelectroless plating can be carried out at room temperature for severalseconds and up to several hours depending upon the desired depositionrate and plating rate and plating metal thickness.

Other useful aqueous-based electroless plating solutions or bathscomprise silver(I) with EDTA and sodium tartrate, silver(I) with ammoniaand glucose, copper(II) with EDTA and dimethylamineborane, copper(II)with citrate and hypophosphite, nickel(II) with lactic acid, aceticacid, and a hypophosphite, and other industry standard aqueous-basedelectroless baths or solutions such as those described by Mallory et al.in Electroless Plating: Fundamentals and Applications 1990.

After the electroless plating procedure to provide anelectrically-conductive pattern on one or more portions of one or bothsupporting sides of the substrate, the resulting product article can beremoved from the aqueous-based electroless plating bath or solution andwashed using distilled water or deionized water or another aqueous-basedsolution to remove any residual electroless plating chemistry. At thispoint, the electrolessly plated metal(s) is generally stable and can beused for their intended purpose to form various electrically-conductivearticles with desired electrically-conductive metal patterns.

In some embodiments, the resulting product article can be rinsed orcleaned with water at room temperature as described for example in[0048] of US 2014/0071356 (Petcavich), or with deionized water at atemperature of less than 70° C. as described in [0027] of WO 2013/169345(Ramakrishnan et al.).

To change the surface of the electroless plated metal for visual ordurability reasons, it is possible that a variety of post-treatments canbe employed including surface plating of still at least another (thirdor more) metal such as nickel or silver on the electrolessly platedmetal (this procedure is sometimes known as “capping”), or the creationof a metal oxide, metal sulfide, or a metal selenide layer that isadequate to change the surface color and scattering properties withoutreducing the conductivity of the electrolessly plated (second) metal.Depending upon the metals used in the various capping procedures of themethod, it may be desirable to treat the electrolessly plated metal withanother seed metal catalyst in an aqueous-based seed metal catalystsolution to facilitate deposition of additional metals.

In addition, multiple treatments with an aqueous-based electroless metalplating solution can be carried out in sequence, using the same ordifferent conditions. Sequential washing or rinsing steps can be alsocarried out where appropriate at room temperature or a temperature lessthan 70° C.

Further, the electroless plating procedures can be carried out multipletimes, in sequence, using the same or different electroless platingmetal and the same or different electroless plating conditions.

Some details of useful methods and apparatus for carrying out someembodiments of the present invention are described for example in US2014/0071356 (noted above) and WO 2013/169345 (noted above). Otherdetails of a useful manufacturing system for preparing conductivearticles especially in a roll-to-roll manner are provided inPCT/US/062366 (filed Oct. 29, 2012 by Petcavich and Jin), the disclosureof which is incorporated herein by reference.

An additional system of equipment and step features that can be used incarrying out the present invention is described in U.S. Ser. No.14/146,867 (filed Jan. 3, 2014 by Shifley), the disclosure of which isincorporated herein by reference for any details that are pertinent tosuch equipment and methods.

The photocurable compositions described herein can be used in a methodto provide one or more electrically conductive articles. This methodcomprises providing a continuous web of a transparent substrate[examples of which are described above, and can be particularlycontinuous webs of poly(ethylene terephthalate)].

On at least a first portion of the continuous web of a transparentsubstrate, the method also includes forming a photocurable pattern of aphotocurable composition (as described herein) that comprises aphotocurable component and dispersed metal particles as described above.The photocurable pattern is then photocured to form a photocured patternon the first portion of the continuous web, which photocured patterncomprises dispersed metal particles (described above) as seed metalcatalyst sites. Such photocured pattern can then be electrolessly platedon the first portion of the continuous web with an electricallyconductive metal (as described above).

This method can further comprise:

carrying out the forming, photocuring, and electrolessly platingfeatures described above one or more additional times on one or moreadditional portions of the continuous web that are different from thefirst portion, using the same or different photocurable composition. Insuch manner, multiple photocured and electrolessly plated patterns canbe formed on the same or different supporting sides of the substrate.The resulting electrically-conductive patterns can be the same incomposition, pattern, or electrical-conductivity, or they can be alldifferent (as predetermined from customer needs) in any or all of thesefeatures. Such multiple electroless plate patterns can be formed asmultiple electrically-conductive grids and multipleelectrically-conductive connectors connected thereto, respectively, oneach of the multiple portions on the one or both supporting sides of thetransparent polymeric web. As noted below in more detail, a dryoutermost polymeric coating can be formed on at least part but not allof each electrically-conductive pattern in any of the multiple portions.The electrically-conductive metal patterns formed in this manner oneither or both the first supporting side and the opposing secondsupporting side of the transparent substrate, can compriseelectrically-conductive metal wires comprise of silver, copper,palladium, or platinum, or two or more of such metals.

Thus, the method of this invention can be used to provide a plurality ofprecursor articles, comprising:

forming a first photocurable pattern on a first portion of thecontinuous web by applying a photocurable composition to the firstportion using a flexographic printing member,

advancing the continuous web comprising the first photocurable patternto be proximate exposing radiation, and thereby forming a firstphotocured pattern on the first portion,

forming a second photocurable pattern on a second portion of thecontinuous web by applying the same or different photocurablecomposition to the second portion using the flexographic printingmember,

advancing the continuous web comprising the second photocurable patternto be proximate exposing radiation, and thereby forming a secondphotocured pattern on the second portion,

optionally, forming one or more additional photocured patterns in asimilar manner on one or more additional respective portions of thecontinuous web using the same or different photocurable composition andthe same or different flexographic printing member, and

winding up the continuous web comprising multiple photocured patterns,or using the continuous web immediately for further processing such aselectrolessly plating and providing the dry outermost polymeric coatingsbefore assembly into electronic devices.

Thus, the method can further comprise:

forming multiple electrically conductive articles from the continuousweb comprising multiple photocured patterns,

forming a dry outermost polymeric coating over at least part but not allof each of the multiple photocured patterns (as described herein), and

assembling the individual electrically conductive articles into the sameor different individual electronic devices (such as the same ordifferent touch screen displays or devices).

Such method can also comprise:

electrolessly plating each of the multiple photocuredelectrically-conductive patterns in the continuous web to form multipleelectrically-conductive articles, and forming the desired dry outermostpolymeric coatings, and the resulting electrically-conductive articlescan be assembled into the same or different individual electronicdevices by the same or different user. Such electronic devices can betouch screen or other display devices that also include suitablecontrollers, housings, and software for any type of desiredcommunication via the Internet. Alternatively, the electronic devicescan be sub-components of such touch screen or other display devices. Insome embodiments, the electronic devices provided by the presentinvention are touch screens each of which has a viewing area of at least1 cm² and up to and including 100 m². The size and shape of the touchscreens can vary depending upon the intended use.

In some embodiments, the method of this invention can be used forpreparing an electronic device comprising a touch screen, the methodcomprising:

assembling one or more individually electrically-conductive articlesinto a device housing to form a touch screen area,

each of the one or more individually electrically-conductive articlescomprising an electrically-conductive pattern comprising anelectrically-conductive metal that has been electrolessly plated onto aphotocured electrically-conductive pattern derived from a photocurablecomposition described herein, and a dry outermost polymeric coating isdisposed over at least part but not all of the electrically-conductivemetal pattern.

The dry outermost polymeric coating described herein can be prepared byfirst dissolving one or more suitable non-crosslinked thermoplasticpolymers in an appropriate solvent (or mixture thereof), followed byprinting or applying the resulting outermost polymeric coatingformulation over a portion of an electrically-conductive pattern.Suitable non-crosslinked thermoplastic polymers include those describedin detail above including, for example, copolymers derived from methylmethacrylate and any of n-butyl methacrylate, iso-butyl methacrylate andn-butyl methacrylate, or terpolymers derived from methyl methacrylate,2-ethylhexyl methacrylate, and methacrylic acid, in appropriate molarratios described above.

Appropriate solvents for the non-crosslinked thermoplastic polymerinclude, but are not limited to, alcohols, ethers, and glycol etherssuch as dipropylene glycol methyl ether, 1-methoxy-2-propanol, and2-methoxy-1-methylethyl acetate. Other materials may be added to theoutermost polymeric coating formulation to give it desired properties,and such materials can be used for controlling viscosity or they can besurfactants for modifying surface tension.

According to the present invention, the outermost polymeric coatingformulation can be deposited over at least a portion of anelectrically-conductive pattern on one or both supporting sides of asubstrate using various deposition or printing techniques known in theart. Such techniques include but are not limited to, flexographicprinting, screen printing, gravure printing, inkjet printing, and slotdie deposition. The deposition method can be used to apply the outermostpolymeric coating formulation in either a one electrically-conductivepattern at a time (for example, a batch process) or over multipleelectrically-conductive patterns in a continuous roll-to-roll process.

Useful product articles prepared according to the present invention canbe formulated into capacitive touch screen sensors that comprisesuitable patterns of electrically-conductive metal patterns and theinventive dry outermost polymeric coatings. For example,electrically-conductive metal grids and electrically-conductive metalconnectors can be formed in the electrically-conductive patterns byprinting a photocurable composition in predetermined patterns, followedby electrolessly plating the printed patterns with suitable metals asdescribed above. The dry outermost polymeric coating formulation canalso be applied over the electrically-conductive metal patterns onlyusing flexographic printing as described above.

The present invention provides at least the following embodiments andcombinations thereof, but other combinations of features are consideredto be within the present invention as a skilled artisan would appreciatefrom the teaching of this disclosure:

1. An electronic device comprising a touch screen comprising atransparent substrate having a first supporting side and an opposingsecond supporting side,

the touch screen comprising on at least the first supporting side:

at least one electrically-conductive pattern, and

a dry outermost polymeric coating disposed over at least part but notall of the electrically-conductive metal pattern, the dry polymericcoating having a dry thickness of less than 5 μm, an integratedtransmittance of at least 80%, and comprising a non-crosslinkedthermoplastic polymer having a glass transition temperature (T_(g)) thatis equal to or greater than 65° C.

2. The electronic device of embodiment 1, wherein the non-crosslinkedthermoplastic polymer is a non-crosslinked thermoplastic acrylicpolymer.

3. The electronic device of embodiment 1 or 2, wherein the dry outermostpolymeric coating has a dry thickness of less than 3 μm.

4. The electronic device of any of embodiments 1 to 3, wherein thenon-crosslinked thermoplastic polymer is a polymer comprising at leastrecurring units derived from methyl (meth)acrylate and recurring unitsderived from an alkyl (meth)acrylate wherein the alkyl has 1 to 18carbon atoms, wherein the recurring units derived from the alkyl(meth)acrylate comprise at least 5 mol % and up to and including 25 mol% of the total polymer recurring units.

5. The electronic device of any of embodiments 1 to 4, wherein theelectrically-conductive pattern disposed on at least the firstsupporting side comprises electrically-conductive metal wires composedof at least silver, copper, palladium, or platinum.

6. The electronic device of any of embodiments 1 to 5, wherein theelectrically-conductive pattern disposed on at least the firstsupporting side comprises at least:

an electrically-conductive grid, and

an electrically-conductive connector that is connected to theelectrically-conductive grid.

7. The electronic device of any of embodiments 1 to 6, wherein the touchscreen has a viewing area of at least 1 cm² and up to and including 100m².

8. The electronic device of any of embodiments 1 to 7, comprising anelectrically-conductive pattern disposed on the opposing secondsupporting side of the transparent substrate, and a dry outermostpolymeric layer that is disposed over at least part but not all of theelectrically-conductive pattern on the opposing second supporting side,the dry outermost polymeric coating having a dry thickness of less than5 μm, an integrated transmittance of at least 80%, and comprising anon-crosslinked thermoplastic polymer having a glass transitiontemperature (T_(g)) that is equal to or greater than 65° C.

9. The electronic device of embodiment 8, wherein the non-crosslinkedthermoplastic polymer on the opposing second supporting side is anon-crosslinked thermoplastic acrylic polymer.

10. The electronic device of embodiment 8 or 9, wherein the dryoutermost polymeric coating on the opposing second supporting side has adry thickness of less than 3 μm.

11. The electronic device of any of embodiments 8 to 10, wherein thenon-crosslinked thermoplastic polymer on the opposing second supportingside is a polymer comprising at least recurring units derived frommethyl (meth)acrylate and recurring units derived from an alkyl(meth)acrylate wherein the alkyl has 1 to 18 carbon atoms, wherein therecurring units derived from the alkyl (meth)acrylate comprise at least5 mol % and up to and including 25 mol % of the total polymer recurringunits.

12. The electronic device of any of embodiments 8 to 11, wherein theelectrically-conductive pattern disposed on the opposing secondsupporting side comprises electrically-conductive metal wires composedof at least silver, copper, palladium, or platinum.

13. The electronic device of any of embodiments 8 to 12, wherein theelectrically-conductive pattern disposed on the opposing secondsupporting side comprises at least:

an electrically-conductive grid, and

an electrically-conductive connector that is connected to theelectrically-conductive grid.

14. The electronic device of any of embodiments 1 to 13, comprising:

two or more of the same or different electrically-conductive patterns oneither or both of the first supporting side and the opposing secondsupporting side, and

the same or different dry outermost polymeric layer disposed over atleast part but not all of each of the two or moreelectrically-conductive patterns, each of the dry outermost polymericcoatings having a dry thickness of less than 5 μm, an integratedtransmittance of at least 80%, and comprising the same or differentnon-crosslinked thermoplastic polymer having a glass transitiontemperature (T_(g)) that is equal to or greater than 65° C.

The following Examples are provided to illustrate the practice of thisinvention and are not meant to be limiting in any manner.

Representative Photocurable Composition 1:

This representative photocurable composition comprised at least thefollowing components formed into a 100 g aliquot:

14.4 g of epoxy acrylates (CN 153 from Sartomer), 9.9 g of poly(ethyleneglycol)diacrylate (M_(n) of 258, Sigma-Aldrich), 2.1 g of poly(ethyleneglycol)diacrylate (M_(n) of 575, Sigma-Aldrich), 10.8 g ofpentaerythritol tetraacrylate (Sigma-Aldrich), 0.8 g of triarylsulfonium salt hexafluorophosphate mixed in 50% propylene carbonate(Sigma-Aldrich), 0.8 g of triaryl sulfonium salt hexafluoroantimonatemixed in 50% propylene carbonate (Sigma-Aldrich), 2.4 g of free radicalphotoinitiator hydroxycyclohexyl phenyl ketone (Sigma-Aldrich), 1.2 g offree radical photoinitiatormethyl-4′-(methylthio)-2-morpholinopropiophenone (Sigma-Aldrich), 19.5 gof “seed” silver particles (from NovaCentrix, 20-25 nm average particlesize, Ag-25-ST3), 1.1 g of carbon particles (US1074 from US Nano), 0.001g of 9-fluorenone (Sigma-Aldrich), and 35 g of 1-methoxy isopropanol(Sigma-Aldrich) solvent.

Printing the Photocurable Composition:

Samples of printed patterns of the photocurable composition describedabove on various primed poly(ethylene terephthalate) PET substrates(MELLINEX® 561 available from DuPont Teijin Films) were obtained using abenchtop test printer, “IGT F1 Printability Tester” (from IGT TestingSystems Inc., Arlington Heights, Ill.) in the flexographic mode. TheAnilox roller system that was used to apply the photocurable compositionto flexographic printing plates had values of 1.3 BCMI and 1803 lpi, asspecified by IGT. The printed patterns were formed at ambienttemperature using an Anilox force of 20 N, a print force of 10 N, and aprint speed of 0.20 m/sec.

The flexographic printing plates used for printing the photocurablecomposition were samples of the commercially available KODAK® Flexcel NXphotopolymer plates (from Eastman Kodak Company) that had been UVradiation imaged using a mask that had a predetermined pattern writtenusing the KODAK® SQUARE SPOT laser technology at a resolution of 12,800dpi. The exposed flexographic photopolymer plates were processed(developed) using known conditions suggested by the manufacturer. Theresulting flexographic printing plates (or members) were each 1.14 mmthick (including the PET). The backing tape used to mount eachflexographic printing plate to the printing form cylinder was the 1120Beige tape from 3M Company, which was 20 mil (0.051 cm) thick with aShore A value of 55. The relief image design in the flexographicprinting plates included a grid pattern with fine lines that had a widthat the top relief surface of 7 μm. The resulting corresponding printedphotocurable composition pattern had average line widths disposed on theprimed PET substrates.

After being applied to the substrate, each printed pattern ofphotocurable composition (that is, the printed pattern) was irradiatedwith UV radiation using a Fusion 300 WPI medium pressure mercury lampproviding irradiation wavelengths between 190-1500 nm, with anapproximate exposure of 298 mJ/cm² to photocure each printed pattern.The printed average line widths of the resulting photocured patterns inthe resulting precursor articles were measured in both transmission andreflection mode using an Olympus BH-2 optical microscope.

Electroless Metal Plating:

Precursor articles comprising the photocured patterns on the variousprimed substrates were electrolessly copper plated by immersing theprecursor articles with the cured patterns for 7 minutes at 45° C. in abeaker containing Enplate Cu-406 electroless plating solution (ENTHONE®Company), followed by rinsing with distilled water and drying withnitrogen, to form articles with electrically-conductive patternsdisposed on the substrates.

Outermost Polymeric Coating Formulation:

An outermost polymeric coating formulation was prepared to have 10weight % of ELVACITE® 4028 resin (Lucite International) in1-methoxy-2-propanol (DOWANOL® PM organic solvent). The formulation wasclear and had a viscosity of 25 cps at 22° C.

Printing the Outermost Polymer Coating Formulation:

Dry outermost polymeric coatings were provided according to the presentinvention by using a flexographic printing press (Performance Series P7available from Mark Andy Inc.) in a continuous roll-to-roll operation,and a single flexographic station. This flexographic station comprised atray that was charged with 300 grams of the outermost polymer coatingformulation, an elastomeric metering roller with a hardness ofapproximately 30 Shore A, a ceramic Anilox roller with a steel doctorblade, and a flexographic plate roller. In this process, the outermostpolymer coating formulation was delivered to the Anilox roller from thetray by the elastomeric metering roll. Excess outermost polymer coatingformulation was removed from the Anilox roller by the steel doctorblade. The Anilox roller system had a value of 2.0 BCMI (billion of μm³per in²) that is equivalent to 0.31 billion of μm³ per cm².

The outermost polymeric coating formulation was then transferred to aflexographic printing plate obtained as described below and thentransferred to a moving web containing the electrolessly metal platedelectrically-conductive patterns described above in a continuous webprocess. All printing, drying, and wind-up operations were performed at18° C. and 50% relative humidity at a line speed of 0.10 m/sec. Thefinal dried electrically-conductive article had a dry outermostpolymeric coating disposed over at least part but not all of eachelectrically-conductive pattern, which dry coating was 0.3 μm inthickness.

The flexographic printing plate used for applying (printing) theoutermost polymeric coating formulation had been formed from acommercially available KODAK® Flexcel NX photopolymer plate (EastmanKodak Company) that had been imaged using a mask that had apredetermined pattern written using the KODAK® SQUARE SPOT lasertechnology at a resolution of 12,800 dpi. The UV-exposed flexographicphotopolymer plate was processed (developed) using known conditionssuggested by the manufacturer. The resulting flexographic printing platewas approximately 1 mm thick. The surface of the flexographic printingplate was left smooth (i.e. as received) except for a rectangular reliefregion (2×35 mm) in the area indexed to the outermost portion of theelectrically-conductive patterns. This relief area did not receive (orconvey) the outermost polymeric coating formulation and, consequently,left a small portion of each electrically-conductive pattern “open”(uncoated) in the resulting electrically-conductive article. Thisuncoated region corresponds to the region where theelectrically-conductive connectors were printed.

Environmental Exposure of Samples:

All electrically-conductive articles prepared as described above wereincubated in an environmental chamber maintained at 65° C. and 90% RH(relative humidity) for four weeks. The electrically-conductive articleswere hung vertically in the environmental chamber and removed at varioustime intervals for assessment of electrical properties.

Measurement of Electrical Continuity:

The electrically-conductive pattern of this electrically-conductivearticle included multiple networks of electrically-conductive grids,wherein the end points of each network of electrically-conductive gridswere connected to two probe-pads, one probe-pad (the near probe-pad) wasconnected to the BUS electrically conductive line, which in turn can beconnected to the “connector” bond-pad that will be connected to anexternal circuit. A “connector” may be comprised of multiple connectorbond-pads. The second probe-pad (the far probe-pad) is connected to theelectrically-conductive grid at the furthest point of the electricalpath from the “connector” bond-pad. For the present example, theconnector bond-pads were not coated with the outermost polymeric coatingformulation so as to provide a connector that would be available tomeasure electrical resistance.

The incubated electrically-conductive articles described above weretested for electrical continuity by applying a pulsed voltage (25 voltsDC) to each electrically-conductive connector in eachelectrically-conductive pattern and measuring the electrical currentbetween the connector bond-pad and the corresponding end probe-pad.Thus, the current pathway was from the external circuit to the connectorbond-pad, through the BUS line, through the near probe-pad, through thenetwork of electrically-conductive grids (approximately 300 mm inlength), and to the end probe-pad. Electrically resistance was thendetermined using Ohm's Law. A resistance of greater than 1000 ohmsthrough this pathway was considered a failure and was considered “open”.For each electrically-conductive article used in these Examples, therewere 34 bonding pad sites and 34 lattice row networks. Thus, the maximumnumber of possible “open” results per electrically-conductive article(and thus, each electrically-conductive pattern) was 34.

Measurement of Transparency:

Transparency of each electrically-conductive article was evaluated bymeasuring the integrated transmittance of radiation at 550 nm asdescribed above.

Comparative Example

Three electrically-conductive articles prepared as described above weresent through the noted flexographic printing press without theapplication of the outermost polymeric coating formulation. Theresulting Comparative electrically-conductive articles, therefore, didnot comprise a dry outermost polymeric coating over theelectrically-conductive patterns. Each Comparativeelectrically-conductive article was subsequently tested for initialelectrical continuity as described above. The initial average integratedtransmittance for each of the three Comparative electrically-conductivearticles was 84%.

The Comparative articles were then incubated in the environmentalchamber and periodically removed for evaluation of electrical continuityas described above for the Invention electrically-conductive articles.TABLE I below shows the increase in the number of “open” evaluations forthe Comparative articles. As shown in TABLE I, the average number of“open” evaluations progressively increased by five perelectrically-conductive article over the four-week incubation period.

Invention Example

Nine electrically-conductive articles prepared as described above weresent through the noted flexographic printing press with the printingstation containing the outermost polymeric coating formulation fullyengaged. Thus, each of these Invention electrically-conductive articlescomprised a dry outermost polymeric coating applied over theelectrically-conductive pattern including the electrically-conductivemetal grids, except for a small rectangular region (2 mm×35 mm) of theelectrically-conductive pattern. The dry thickness of the outermostprotective coating was 0.3 μm. The initial integrated transmittance ofall nine electrically-conductive articles was determined to be 84%.

The Invention articles were incubated in the environmental chamber andperiodically removed for evaluation of electrical continuity asdescribed above. TABLE I below shows the increase in the number of“open” evaluations for the Invention electrically-conductive articles.As shown in TABLE I, the average number of “open” evaluations did notincrease over the four week incubation period. Thus, the dry outermostpolymeric coating disposed over at least part but not all of theelectrically-conductive pattern in each electrically-conductive articlewas determined to provide good protection of the electrically-conductivepatterns against contaminates (for example, water and oxygen) even underharsh environmental conditions.

TABLE I Control Electrically- Invention Electrically- conductiveArticles conductive Articles Time Into Incubation (number of “open”(number of “open” (days) evaluations) evaluations) 0 0 0 2 2 0 7 2 0 143 0 28 5 0

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

1. An electronic device comprising a touch screen comprising atransparent substrate having a first supporting side and an opposingsecond supporting side, the touch screen comprising on at least thefirst supporting side: at least one electrically-conductive pattern, anda dry outermost polymeric coating disposed over at least part but notall of the electrically-conductive metal pattern, the dry polymericcoating having a dry thickness of less than 5 μm, an integratedtransmittance of at least 80%, and comprising a non-crosslinkedthermoplastic polymer having a glass transition temperature (T_(g)) thatis equal to or greater than 65° C.
 2. The electronic device of claim 1,wherein the non-crosslinked thermoplastic polymer is a non-crosslinkedthermoplastic acrylic polymer.
 3. The electronic device of claim 1,wherein the dry outermost polymeric coating has a dry thickness of lessthan 3 μm.
 4. The electronic device of claim 1, wherein thenon-crosslinked thermoplastic polymer is a polymer comprising at leastrecurring units derived from methyl (meth)acrylate and recurring unitsderived from an alkyl (meth)acrylate wherein the alkyl has 1 to 18carbon atoms, wherein the recurring units derived from the alkyl(meth)acrylate comprise at least 5 mol % and up to and including 25 mol% of the total polymer recurring units.
 5. The electronic device ofclaim 1, wherein the electrically-conductive pattern disposed on atleast the first supporting side comprises electrically-conductive metalwires composed of at least silver, copper, palladium, or platinum. 6.The electronic device of claim 1, wherein the electrically-conductivepattern disposed on at least the first supporting side comprises atleast: an electrically-conductive grid, and an electrically-conductiveconnector that is connected to the electrically-conductive grid.
 7. Theelectronic device of claim 1, wherein the touch screen has a viewingarea of at least 1 cm² and up to and including 100 m².
 8. The electronicdevice of claim 1, comprising an electrically-conductive patterndisposed on the opposing second supporting side of the transparentsubstrate, and a dry outermost polymeric layer that is disposed over atleast part but not all of the electrically-conductive pattern on theopposing second supporting side, the dry outermost polymeric coatinghaving a dry thickness of less than 5 an integrated transmittance of atleast 80%, and comprising a non-crosslinked thermoplastic polymer havinga glass transition temperature (T_(g)) that is equal to or greater than65° C.
 9. The electronic device of claim 8, wherein the non-crosslinkedthermoplastic polymer on the opposing second supporting side is anon-crosslinked thermoplastic acrylic polymer.
 10. The electronic deviceof claim 8, wherein the dry outermost polymeric coating on the opposingsecond supporting side has a dry thickness of less than 3 μm.
 11. Theelectronic device of claim 8, wherein the non-crosslinked thermoplasticpolymer on the opposing second supporting side is a polymer comprisingat least recurring units derived from methyl (meth)acrylate andrecurring units derived from an alkyl (meth)acrylate wherein the alkylhas 1 to 18 carbon atoms, wherein the recurring units derived from thealkyl (meth)acrylate comprise at least 5 mol % and up to and including25 mol % of the total polymer recurring units.
 12. The electronic deviceof claim 8, wherein the electrically-conductive pattern disposed on theopposing second supporting side comprises electrically-conductive metalwires composed of at least silver, copper, palladium, or platinum. 13.The electronic device of claim 8, wherein the electrically-conductivepattern disposed on the opposing second supporting side comprises atleast: an electrically-conductive grid, and an electrically-conductiveconnector that is connected to the electrically-conductive grid.
 14. Theelectronic device of claim 1, comprising: two or more of the same ordifferent electrically-conductive patterns on either or both of thefirst supporting side and the opposing second supporting side, and thesame or different dry outermost polymeric layer disposed over at leastpart but not all of each of the two or more electrically-conductivepatterns, each of the dry outermost polymeric coatings having a drythickness of less than 5 μm, an integrated transmittance of at least80%, and comprising the same or different non-crosslinked thermoplasticpolymer having a glass transition temperature (T₅) that is equal to orgreater than 65° C.